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1.

What will be the area of the quadrilateral ABCD whose vertices are A (8, 6), B (9, 0), C (1, 2) and D (3, 4)?(a) -20 units(b) 26 units(c) 23 units(d) 3 unitsThe question was asked in an online quiz.I'm obligated to ask this question of Geometry in section Coordinate Geometry of Mathematics – Class 10

Answer»

Correct ANSWER is (b) 26 units

Easiest EXPLANATION: Area of quadrilateral = Area of ∆ABC + Area of ∆ADC

We know that, area of triangle = \(\frac {1}{2}\){x1 (y2 – y3) + x2(y3 – y1) + x3(y1 – y2)}

The coordinates of VERTICES of the triangle are (8, 6), (9, 0) and (1, 2).

The area of triangle = \(\frac {1}{2}\){8(0 – 2) + 9(2 – 6) + 1(6 – 0)} = \(\frac {1}{2}\) { – 16 – 36 + 6} = \(\frac {-46}{2}\) = – 23 units

The area of triangle cannot be zero. So, Area of ∆ABC = 23 units

We know that, area of triangle = \(\frac {1}{2}\){x1(y2 – y3) + x2(y3 – y1) + x3 (y1 – y2)}

The coordinates of vertices of the triangle are (8, 6), (3, 4) and (1, 2).

The area of triangle = \(\frac {1}{2}\) {8(4 – 2) + 3(2 – 6) + 1(6 – 4)} = \(\frac {1}{2}\) {16 – 12 + 2} = \(\frac {6}{2}\) = 3 units

So, Area of ∆ADC = 3 units

Area of quadrilateral = Area of ∆ABC + Area of ∆ADC = 23 + 3 = 26 units

2.

What will be the value of x, if the distance between the points (5, 11) and (2, x) is 10?(a) -11 + √91, -11 – √91(b) 11 + √91, 11 – √91(c) 11 + √91, 11 + √91(d) -11 + √91, 11 – √91The question was asked in a national level competition.This question is from Geometry in division Coordinate Geometry of Mathematics – Class 10

Answer»

Right option is (b) 11 + √91, 11 – √91

The EXPLANATION is: Distance between (5, 11) and (2, x) = \( \sqrt {(x_2-x_1)^2 + (y_2-y_1)^2} \)

= \( \sqrt {(2-5)^2 + (x-11)^2} \)

= \( \sqrt {x^2-22X + 121 + (-3)^2} \)

= \( \sqrt {x^2-22x + 121 + 9} \)

= \( \sqrt {x^2-22x + 130} \)

The distance between (5, 11) and (2, x) is 10

∴ \( \sqrt {x^2-22x + 130} \) = 10

Squaring on both sides we get,

x^2 – 22x + 130 = 100

x^2 – 22x + 130 – 100 = 0

x^2 – 22x + 30 = 0

x = 11 + √91, 11 – √91

3.

What will be the coordinates of B, if the point C\((\frac {29}{7}, \frac {46}{7} )\), divides the line segment joining A (5, 8) and B (a, b) in the ratio 2:5?(a) a = 2, b = 3(b) a = -2, b = 3(c) a = 2, b = -3(d) a = -2, b = -3I got this question during an online interview.The above asked question is from Geometry in portion Coordinate Geometry of Mathematics – Class 10

Answer»

Correct answer is (a) a = 2, b = 3

To explain I would say: Using, section formula x = \(\frac {mx_2+nx_1}{m+n}\) and y = \(\frac {my_2+ny_1}{m+n}\)

The POINTS are A(5, 8)and B(a, b)in the ratio 2:5

∴ x = \(\frac {2(a)+5(5)}{2+5} = \frac {2a+25}{7}\)

y = \(\frac {2(b)+5(8)}{2+5} = \frac {2b+40}{7}\)

But the COORDINATES of C are \((\frac {29}{7}, \frac {46}{7} )\)

Therefore, \(\frac {2a+25}{7} = \frac {29}{7}\)

a = 2

\(\frac {2b+40}{7} = \frac {46}{7}\)

b = 3

4.

What will be the area of triangle formed by joining the points P (2, 3), Q (4, 6) and R (6, 9)?(a) 0(b) 2(c) 3(d) 4The question was asked in an online interview.My doubt stems from Geometry topic in division Coordinate Geometry of Mathematics – Class 10

Answer» CORRECT CHOICE is (a) 0

Easy explanation: We know that, area of TRIANGLE = \(\FRAC {1}{2}\){x1 (y2 – y3 ) + x2 (y3 – y1 ) + x3 (y1 – y2 )}

Let US assume the vertices of the triangle are (2, 3), (4, 6) and (6, 9).

The area of triangle = \(\frac {1}{2}\) {2(6 – 9) + 4(9 – 3) + 6(3 – 6) } = \(\frac {1}{2}\){0} = 0 units

Hence, the area of triangle is zero, the points are collinear.
5.

In what ratio does the point (\(\frac {-19}{3}, \frac {7}{3}\)) divide the line segment joining A(3, 7) and B(-11, 0)?(a) 1:2 (externally)(b) 1:2 (internally)(c) 2:1 (externally)(d) 2:1 (internally)The question was posed to me in an international level competition.The origin of the question is Geometry topic in portion Coordinate Geometry of Mathematics – Class 10

Answer»

Right answer is (d) 2:1 (internally)

For EXPLANATION I WOULD say: Let the ratio in which the point (\(\frac {-19}{3}, \frac {7}{3}\)) divides the LINE segment joining the POINTS A(3, 7) and B(-11, 0) be k:1

Using, section formula x = \(\frac {mx_2+nx_1}{m+n}\) and y = \(\frac {my_2+ny_1}{m+n}\)

The points are A(3, 7) and B(-11, 0) and the ratio is k:1

∴ x = \(\frac {k(-11)+1(3)}{k+1} = \frac {-11k+3}{k+1}\)

y = \(\frac {k(0)+1(7)}{k+1} = \frac {7}{k+1}\)

Since, the point is (\(\frac {-19}{3}, \frac {7}{3}\)).

∴ \(\frac {-19}{3} = \frac {-11k+3}{k+1}\)

-19(k + 1) = 3(-11k + 3)

-19k – 19 = -33k + 9

-19k + 33k = 19 + 9

14k = 28

k = \(\frac {28}{14}\) = 2

The ratio is 2:1.

6.

If the points A (a, 0), B (0, b) and C (c, 0) are collinear then a = -c.(a) False(b) TrueI have been asked this question in quiz.The question is from Geometry in section Coordinate Geometry of Mathematics – Class 10

Answer»

The correct option is (a) False

For EXPLANATION: We know that, area of triangle = \(\frac {1}{2}\){x1(Y2 – y3 ) + x2(y3 – y1 ) + x3(y1 – y2 )}

The three points are A (a, 0), B (0, b) and C (c, 0)

Since the points are collinear, the area of triangle will be zero.

The area of triangle = \(\frac {1}{2}\) {a(b – 0) + 0(c – 0) + c(0 – b) } = \(\frac {1}{2}\) {ab + 0 – bc}

\(\frac {1}{2}\) {ab – bc} = 0

{ab – bc} = 0

a = c

7.

What will be the value of a and b, if (-5, a), (-3, -3), (-b, 0) and (-3, 3) are the vertices of the parallelogram?(a) a = 0, b = -1(b) a = -1, b = 1(c) a = 1, b = 1(d) a = 0, b = 1This question was posed to me in an international level competition.The above asked question is from Geometry topic in section Coordinate Geometry of Mathematics – Class 10

Answer»

Correct answer is (d) a = 0, B = 1

The best EXPLANATION: PQRS is a parallelogram. The opposite side of the parallelogram is equal and parallelogram. Also, the diagonals of the parallelogram BISECT each other.

∴ O is the mid-point SQ and PR.

Midpoint of PR

Using, section formula x = \(\frac {mx_2+nx_1}{m+n}\) and y = \(\frac {my_2+ny_1}{m+n}\)

The points are P(-5, a) and R(-b, 0) and the ratio is 1:1

∴ x = \(\frac {1(-b)+1(-5)}{2} = \frac {-b-5}{2}\)

y = \(\frac {1(0)+1(a)}{2} = \frac {a}{2}\)

Midpoint of QS

Using, section formula x = \(\frac {mx_2+nx_1}{m+n}\) and y = \(\frac {my_2+ny_1}{m+n}\)

The points are Q(-3, -3) and S(-3, 3) and the ratio is 1:1

∴ x = \(\frac {1(-3)+1(-3)}{2} = \frac {-6}{2}\) = -3

y = \(\frac {1(3)+1(-3)}{2} = \frac {0}{2}\) = 0

Therefore, \(\frac {-b-5}{2}\) = -3

b = 1

\(\frac {a}{2}\) = 0

a = 0

8.

What will be the point of y-axis which will be equidistant from the points (-1, 0) and (3, 9)?(a) (5, \( \frac {89}{18} \))(b) (1, \( \frac {89}{18} \))(c) (16, \( \frac {89}{18} \))(d) (0, \( \frac {89}{18} \))I got this question in an online quiz.My question is taken from Geometry topic in section Coordinate Geometry of Mathematics – Class 10

Answer»

Right OPTION is (d) (0, \( \FRAC {89}{18} \))

To EXPLAIN I would say: LET the point on y-axis be (0, y)

Distance between (-1, 0) and (0, y) = \( \SQRT {(x_2-x_1)^2 + (y_2-y_1)^2} \)

= \( \sqrt {(0 + 1)^2 + (y-0)^2} \)

= \( \sqrt {y^2 + (1)^2} \)

= \( \sqrt {y^2 + 1} \)

Distance between (3, 9) and (0, y) = \( \sqrt {(x_2-x_1)^2 + (y_2-y_1)^2} \)

= \( \sqrt {(0-3)^2 + (y-9)^2} \)

= \( \sqrt {y^2-18y + 81 + (-3)^2} \)

= \( \sqrt {y^2-18y + 81 + 9} \)

= \( \sqrt {y^2-18y + 90} \)

Since, the point (0, y) is equidistant from (-1, 0) and (3, 9)

The distances will be equal

∴ \( \sqrt {y^2 + 1} =\sqrt {y^2-18y + 90} \)

Squaring on both sides we get,

y^2 + 1 = y^2 – 18y + 90

1 – 90 = -18y

-89 = -18y

y = \( \frac {89}{18} \)

The point is (0, \( \frac {89}{18} \))

9.

What will be the area of a triangle whose vertices are (3, 1), (0, 4) and (5, 9)?(a) 5 units(b) -5 units(c) -15 units(d) 15 unitsI had been asked this question in an interview for internship.The query is from Geometry in section Coordinate Geometry of Mathematics – Class 10

Answer»

Correct choice is (c) -15 UNITS

To explain I would say: We know that, area of triangle = \(\FRAC {1}{2}\){x1(y2 – Y3) + x2(y3 – y1) + X3(y1 – y2 )}

The coordinates of vertices of the triangle are (3, 1), (0, 4) and (5, 9).

The area of triangle = \(\frac {1}{2}\){3(4 – 9) + 0(9 – 1) + 5(1 – 4) } = \(\frac {1}{2}\) {-15 + 0 – 15} = \(\frac {-30}{2}\) = -15 units

Since area of triangle cannot be zero. So area of triangle is 15 units.

10.

In what ratio is the line segment joining the points A(-5, 2) and B(3, 9) divided by the x-axis?(a) 2:5 (internally)(b) 2:5 (externally)(c) 2:9 (externally)(d) 2:9 (internally)The question was posed to me in final exam.This key question is from Geometry in section Coordinate Geometry of Mathematics – Class 10

Answer»

Right choice is (c) 2:9 (EXTERNALLY)

Easy explanation: Let the ratio in which the x-axis divides the LINE SEGMENT JOINING the points A(-5, 2) and B(3, 9) be k:1

Using, section formula x = \(\frac {mx_2+nx_1}{m+n}\) and y = \(\frac {my_2+ny_1}{m+n}\)

The points are A(-5, 2) and B(3, 9) and the ratio is k:1

∴ x = \(\frac {k(3)+1(-5)}{k+1} = \frac {3k-5}{k+1}\)

y = \(\frac {k(9)+1(2)}{k+1} = \frac {9k+2}{k+1}\)

Since, the point is on x-axis.

Hence, the y-coordinate will be zero.

∴ 0 = \(\frac {9k+2}{k+1}\)

0 = 9k+2

k = \(\frac {-2}{9}\)

The ratio in which the y-axis cuts the line segment joining the points A(-5, 2) and B(3, 9) will be 2:9 (externally).

11.

What will be the coordinates of the point which divides the line segment joining the points A(-2, 2) and B(-1, 5) in the ratio 2:5?(a) (\(\frac {-4}{3}, \frac {-20}{9}\))(b) (\(\frac {-4}{3}, \frac {20}{9}\))(c) (\(\frac {4}{3}, \frac {20}{9}\))(d) (\(\frac {4}{3}, \frac {-20}{9}\))The question was posed to me in class test.The question is from Geometry in section Coordinate Geometry of Mathematics – Class 10

Answer»

Right choice is (b) (\(\frac {-4}{3}, \frac {20}{9}\))

Best explanation: Using, section formula x = \(\frac {mx_2+nx_1}{m+n}\) and y = \(\frac {my_2+ny_1}{m+n}\)

The points are A(-2, 2) and B(-1, 5) and the RATIO is 2:5

∴ x = \(\frac {2(-1)+5(-2)}{2+7} = \frac {-2-10}{9} = \frac {-12}{9} = \frac {-4}{3}\)

y = \(\frac {2(5)+5(2)}{2+7} = \frac {10+10}{9} = \frac {20}{9} = \frac {20}{9}\)

HENCE, the point is (\(\frac {-4}{3}, \frac {20}{9}\)).

12.

In what ratio is the line segment joining the points A(2, 4) and B(6, 5) divided by the y-axis?(a) 2:1 (internally)(b) 2:1 (externally)(c) 3:1 (internally)(d) 3:1 (externally)This question was addressed to me in quiz.I want to ask this question from Geometry in portion Coordinate Geometry of Mathematics – Class 10

Answer»

The CORRECT answer is (d) 3:1 (externally)

Explanation: Let the ratio in which the y-axis divides the line segment joining the points A(2, 4) and B(6, 5) be K:1

Using, section formula x = \(\frac {mx_2+nx_1}{m+n}\) and y = \(\frac {my_2+ny_1}{m+n}\)

The points are A(2, 4) and B(6, 5) and the ratio is k:1

∴ x = \(\frac {k(6)+1(2)}{k+1} = \frac {6K+2}{k+1}\)

y = \(\frac {k(5)+1(4)}{k+1} = \frac {5k+4}{k+1}\)

Since, the point is on y-axis.

Hence, the x-coordinate will be zero.

∴ 0 = \(\frac {6k+2}{k+1}\)

0 = 6k + 2

k = \(\frac {-6}{2}\) = -3

The ratio in which the y-axis CUTS the line segment joining the points A(2, 4) and B(6, 5) will be 3:1 (externally).

13.

What will be the point of x-axis which will be equidistant from the points (9, 8) and (3, 2)?(a) (10, 0)(b) (13, 0)(c) (11, 0)(d) (12, 0)I had been asked this question during an interview.My doubt stems from Geometry in section Coordinate Geometry of Mathematics – Class 10

Answer» RIGHT ANSWER is (c) (11, 0)

The EXPLANATION: Let the point on x-axis be (x, 0)

Distance between (9, 8) and (x, 0) = \( \SQRT {(x_2-x_1)^2 + (y_2-y_1)^2} \)

= \( \sqrt {(x-9)^2 + (0-8)^2} \)

= \( \sqrt {x^2-18x + 81 + (-8)^2} \)

= \( \sqrt {x^2-18x + 81 + 64} \)

= \( \sqrt {x^2-18x + 145} \)

Distance between (3, 2) and (x, 0) = \( \sqrt {(x_2-x_1)^2 + (y_2-y_1)^2} \)

= \( \sqrt {(x-3)^2 + (0-2)^2} \)

= \( \sqrt {x^2-6x + 9 + (-2)^2} \)

= \( \sqrt {x^2-6x + 9 + 4} \)

= \( \sqrt {x^2-6x + 13} \)

Since, the point ( x, 0) is EQUIDISTANT to (3, 2) and (9, 8)

The distances will be equal

∴ \( \sqrt {x^2-18x + 145} = \sqrt {x^2-6x + 13} \)

Squaring on both sides we get,

x^2 – 18x + 145 = x^2 – 6x + 13

-18x + 145 = -6x + 13

-18x + 6x = -145 + 13

-12x = -132

x = \( \frac {132}{12} \) = 11

The point is (11, 0)
14.

The two vertices of ∆ABC are given by A(-3, 0) and B(-8, 5) and its centroid is (-2, 1).What will be the coordinates of the third vertex C?(a) (-5, -2)(b) (5, 2)(c) (-5, 2)(d) (5, -2)This question was addressed to me in examination.My enquiry is from Geometry topic in division Coordinate Geometry of Mathematics – Class 10

Answer»

Right answer is (d) (5, -2)

The best I can EXPLAIN: The two vertices of TRIANGLE are A (-3, 0) and B (-8, 5). Its centroid is (-2, 1).

We KNOW, xcentroid = \(\frac {x_1+x_2+x_3}{3}\) and ycentroid = \(\frac {y_1+y_2+y_3}{3}\)

Now, xcentroid = \(\frac {-3-8+x_3}{3}\)

xcentroid = -2

-2 = \(\frac {-3 – 8 + x_3}{3}\)

-6 = -3 – 8 + x3

5 = x3

Now, ycentroid = \(\frac {0+5+y_3}{3}\)

ycentroid = 1

1 = \(\frac {0 + 5 + y_3}{3}\)

3 = 5 + y3

-2 = y3

The THIRD coordinate is (5, -2).

15.

The points A (3, 0), B (4, 5) and C (6, 7) are collinear.(a) True(b) FalseThe question was posed to me in examination.This intriguing question comes from Geometry topic in division Coordinate Geometry of Mathematics – Class 10

Answer»

The correct option is (b) False

Best explanation: We KNOW that, area of triangle = \(\FRAC {1}{2}\){x1 (y2 – Y3 ) + X2 (y3 – y1 ) + x3 (y1 – y2 )}

Let us assume the vertices of the triangle are A (3, 0), B (4, 5) and C (6, 7)

The area of triangle = \(\frac {1}{2}\) {3(5 – 7) + 4(7 – 0) + 6(0 – 5)} = \(\frac {1}{2}\) {-8} = – 4 units

Since, the area of triangle is not zero.

Therefore, the points are not collinear.

16.

What will be the centroid of the ∆ABC whose vertices are A(-2, 4), B(0, 0) and C(4, 2)?(a) (\(\frac {2}{3}\), 2)(b) (\(\frac {2}{3}\), 1)(c) (\(\frac {2}{5}\), 2)(d) (\(\frac {1}{3}\), 2)This question was addressed to me during an online interview.The query is from Geometry in chapter Coordinate Geometry of Mathematics – Class 10

Answer»

The correct option is (a) (\(\FRAC {2}{3}\), 2)

Explanation: We know, xcentroid = \(\frac {x_1+x_2+x_3}{3}\) and ycentroid = \(\frac {y_1+y_2+y_3}{3}\)

xcentroid = \(\frac {-2+0+4}{3} = \frac {2}{3}\)

ycentroid = \(\frac {4+0+2}{3}\) = 2

The coordinates of the centroid are (\(\frac {2}{3}\), 2).

17.

What will be the coordinates of the midpoint of the line segment joining the points (-5, 10) and(15, 2)?(a) (-5, -6)(b) (-5, 6)(c) (5, 6)(d) (5, -6)I had been asked this question in an international level competition.Enquiry is from Geometry in chapter Coordinate Geometry of Mathematics – Class 10

Answer»

Correct answer is (c) (5, 6)

To explain I would say: Midpoint lies in the center of the LINE segment

Hence, it divides the line in the RATIO 1:1

Using, section formula X = \(\FRAC {mx_2+nx_1}{m+n}\) and y = \(\frac {my_2+ny_1}{m+n}\)

The points are A(-5, 10) and B(15, 2) and the ratio is 1:1

∴ x = \(\frac {1(-5)+1(15)}{2} = \frac {-5+15}{2} = \frac {10}{2}\) = 5

y = \(\frac {1(2)+1(10)}{2} = \frac {2+10}{2} = \frac {12}{2}\) = 6

Hence, the point is (5,6).

18.

The distance of the point (9, -12) from origin will be ___________(a) 13(b) 15(c) 14(d) 17I got this question in quiz.This is a very interesting question from Geometry in chapter Coordinate Geometry of Mathematics – Class 10

Answer» RIGHT choice is (B) 15

To explain I would say: DISTANCE between (9, -12) and (0, 0) = \( \sqrt {(x_2-x_1)^2 + (y_2-y_1)^2} \)

= \( \sqrt {(0-9)^2 + (0 + 12)^2} \)

= \( \sqrt {(9)^2 + (-12)^2} \)

= \( \sqrt {81 + 144}\)

= √225 = 15
19.

The point on y-axis which is at a distance 5 unit from the point (-5, 7) is ___________(a) (7, 0)(b) (0, 7)(c) (1, 7)(d) (7, 7)I had been asked this question during an online exam.My enquiry is from Geometry topic in chapter Coordinate Geometry of Mathematics – Class 10

Answer» RIGHT choice is (B) (0, 7)

Easiest explanation: Let the point on y-axis be (0, y)

Distance between (-5, 7) and (0, y) = \( \sqrt {(x_2-x_1)^2 + (y_2-y_1)^2} \)

= \( \sqrt {(0 + 5)^2 + (y-7)^2} \)

= \( \sqrt {y^2-14y + 49 + 25} \)

= \( \sqrt {y^2-14y + 74} \)

The distance between (-5, 7) and (0, y) is 5

∴ \( \sqrt {y^2-14y + 74} \) = 5

Squaring on both sides, we get,

y^2 – 14y + 74 = 25

y^2 – 14y + 49 = 0

y = 7, 7

Hence, the point is (0, 7)
20.

What will be the value of p, for which the points (-3, p), (-1, 2) and (1, 1) are collinear?(a) p = -4(b) p = 4(c) p = 3(d) p = -3I had been asked this question in unit test.The doubt is from Geometry topic in chapter Coordinate Geometry of Mathematics – Class 10

Answer» RIGHT option is (c) p = 3

The explanation is: We know that, area of triangle = \(\frac {1}{2}\){x1 (y2 – y3 ) + x2 (y3 – y1 ) + x3 (y1 – y2 )}

The VERTICES of the triangle are (-3, p), (-1, 2) and (1, 1)

The area of triangle = \(\frac {1}{2}\) {-3(2 – 1) + (-1)(1 – p) + 1(p – 2)} = \(\frac {1}{2}\) {-3 – 1 + p + p – 2} = \(\frac {-6 + 2p}{2}\) = – 3 + p

Since, the points are collinear; the area of triangle will be zero.

-3 + p = 0

p = 3
21.

What will be the area of triangle PQR formed by joining the midpoints of the sides of the triangle whose vertices are (3, 3), (9, 9) and (4, 6)?(a) \(\frac {1}{2}\) units(b) \(\frac {3}{2}\) units(c) \(\frac {3}{5}\) units(d) \(\frac {5}{2}\) unitsI had been asked this question in quiz.This intriguing question comes from Geometry in portion Coordinate Geometry of Mathematics – Class 10

Answer»

Correct choice is (b) \(\frac {3}{2}\) units

Easiest explanation: ABC is the triangle formed by the coordinates A (3, 3), B (9, 9) and C (4, 6) and DEF is the triangle formed by joining the MIDPOINTS of AC, BC, AB.

D is the midpoint of AC. Coordinates of D = \( ( \frac {x_1+x_2}{2}, \frac {y_1+y_2}{2} ) = ( \frac {3+4}{2}, \frac {3+6}{2} ) = ( \frac {7}{2}, \frac {9}{2} ) \)

E is the midpoint of AB. Coordinates of E = \( ( \frac {x_1+x_2}{2}, \frac {y_1+y_2}{2} ) = ( \frac {3+9}{2}, \frac {3+9}{2} ) = ( \frac {12}{2}, \frac {12}{2} ) \) = (6, 6)

F is the midpoint of BC. Coordinates of F = \( ( \frac {x_1+x_2}{2}, \frac {y_1+y_2}{2} ) = ( \frac {9+4}{2}, \frac {9+6}{2} ) = ( \frac {13}{2}, \frac {15}{2} ) \)

The AREA of triangle formed by D \( ( \frac {7}{2}, \frac {9}{2} ) \), E (6, 6) and F\( ( \frac {13}{2}, \frac {15}{2} ) \)

We know that, area of triangle = \(\frac {1}{2}\){x1 (y2 – y3 ) + X2 (y3 – y1 ) + x3 (y1 – y2 )}

The coordinates of vertices of the triangle are \( ( \frac {7}{2}, \frac {9}{2} ) \), (6, 6) and \( ( \frac {13}{2}, \frac {15}{2} ) \).

The area of triangle = \(\frac {1}{2} \{ \frac {7}{2}\) (6 – \(\frac {15}{2}\)) + 6(\(\frac {15}{2} – \frac {9}{2}\)) + \(\frac {13}{2} ( \frac {9}{2} – 6 ) \} \) = \(\frac {1}{2} \{ – \frac {21}{4}\) + 18 – \(\frac {39}{4} \} = \frac {3}{2} \) units

22.

The distance between the points (5, 7) and (8, -5) is ________(a) √153(b) √154(c) √13(d) √53This question was posed to me in class test.Question is taken from Geometry topic in portion Coordinate Geometry of Mathematics – Class 10

Answer»

The correct answer is (a) √153

The EXPLANATION: Using distance formula,

Distance between (5, 7) and (8, -5) = \( \sqrt {(x_2-x_1)^2 + (y_2-y_1)^2} \)

= \( \sqrt {(8-5)^2 + (-5-7)^2}\)

= \( \sqrt {(3)^2 + (-12)^2} \)

= \( \sqrt {9 + 144}\)

= √153

23.

What will be the coordinates of the fourth vertex S, if P(-1, -1), Q(2, 0), R(2, 3) are the three vertices of a parallelogram?(a) (-5, -12)(b) (5, -12)(c) (5, 12)(d) (-5, 12)I have been asked this question in an international level competition.I need to ask this question from Geometry topic in chapter Coordinate Geometry of Mathematics – Class 10

Answer»

The correct CHOICE is (c) (5, 12)

To explain: PQRS is a parallelogram. The OPPOSITE side of the parallelogram is equal and parallelogram. Also, the diagonals of the parallelogram bisect each other.

∴ O is the mid-point SQ and PR.

MIDPOINT of PR

Using, section formula x = \(\frac {mx_2+nx_1}{m+n}\) and y = \(\frac {my_2+ny_1}{m+n}\)

The points are P(-1, -1) and R(2, 3) and the RATIO is 1:1

∴ x = \(\frac {1(-1)+1(2)}{2} = \frac {-1+2}{2} = \frac {1}{2}\)

y = \(\frac {1(3)+1(-1)}{2} = \frac {3-1}{2} = \frac {2}{2}\) = 1

Hence, the coordinates of O is (5, 6)

Midpoint of QS

Using, section formula x = \(\frac {mx_2+nx_1}{m+n}\) and y = \(\frac {my_2+ny_1}{m+n}\)

The points are Q(2, 0) and S(a, b) and the ratio is 1:1

∴ x = \(\frac {1(a)+1(2)}{2} = \frac {a+2}{2}\)

y = \(\frac {1(b)+1(0)}{2} = \frac {b}{2}\)

The coordinates of O is (5, 6)

Therefore, \(\frac {a+2}{2}\) = 5

a = 8

\(\frac {b}{2}\) = 6, b = 12

The coordinates of S are (5, 12).

24.

What will be the length of the median through the vertex A, if the coordinates of the vertices of∆ABC are A(2, 5), B(5, 0), C(-2, 5)?(a) \(\sqrt {\frac {113}{3}}\) units(b) \(\sqrt {\frac {13}{2}}\) units(c) \(\sqrt {\frac {113}{2}}\) units(d) \(\sqrt {\frac {13}{2}}\) unitsThis question was posed to me at a job interview.This key question is from Geometry topic in chapter Coordinate Geometry of Mathematics – Class 10

Answer» CORRECT choice is (B) \(\SQRT {\frac {13}{2}}\) units

Best explanation: The median through A will BISECT the line BC.

Hence, D is the midpoint of BC

Coordinates of D = \((\frac {x_1+x_2}{2}, \frac {y_1+y_2}{2} ) = ( \frac {5-2}{2}, \frac {0-5}{2} ) =( \frac {3}{2}, \frac {-5}{2} )\)

Distance between A and D = \( \sqrt {(x_2-x_1)^2 + (y_2-y_1)^2} \)

= \( \sqrt {(2-\frac {3}{2})^2+ (5+\frac {5}{2})^2} \)

= \( \sqrt {(\frac {1}{2})^2+ (\frac {15}{2})^2} \)

= \( \sqrt {\frac {1}{4}+ \frac {225}{4}} \)

= \( \sqrt {\frac {113}{2}} \) units
25.

If the points A, B, C is collinear then the area of the triangle will be zero.(a) True(b) FalseI got this question in class test.The above asked question is from Geometry topic in section Coordinate Geometry of Mathematics – Class 10

Answer»

Right choice is (b) False

The best I can explain: We know that, area of TRIANGLE = \(\frac {1}{2}\){X1 (y2 – y3 ) + x2 (y3 – Y1 ) + x3 (y1 – y2 )}

LET us assume the vertices of the triangle are (0, 0), (0, 4) and (0, 9).

The area of triangle = \(\frac {1}{2}\) {0(4 – 9) + 0(9 – 0) + 0(0 – 4) } = \(\frac {1}{2}\){0} = 0 units

Hence, the area of triangle will be zero if the points are collinear.

26.

What will be the value of y, if the ratio in which the point (\(\frac {3}{4}\), y) divides the line segment joining the points A(-1, 4) and B(6, 5)is 1:3?(a) y = \(\frac {9}{2}\)(b) y = \(\frac {5}{2}\)(c) y = \(\frac {9}{4}\)(d) y = \(\frac {5}{2}\)I got this question in an international level competition.My question is based upon Geometry in chapter Coordinate Geometry of Mathematics – Class 10

Answer»

Right option is (a) y = \(\frac {9}{2}\)

The explanation: Using, section formula x = \(\frac {mx_2+nx_1}{m+n}\) and y = \(\frac {my_2+ny_1}{m+n}\)

The points are (-1, 4)and B(6, 5)in the ratio 1:3

∴ x = \(\frac {1(6)+3(-1)}{1+3} = \frac {6-3}{4} = \frac {3}{4}\)

y = \(\frac {1(6)+3(4)}{1+3} = \frac {6+12}{4} = \frac {18}{4}\)

Therefore y = \(\frac {9}{2}\)

27.

The area of the triangle if A (-1, -1), B(-1, 3) and C (2, -1) are the vertices of the triangle is ____________(a) 8 units(b) 4 units(c) 6 units(d) 5 unitsThis question was addressed to me during an online interview.I'd like to ask this question from Geometry topic in division Coordinate Geometry of Mathematics – Class 10

Answer»

Right CHOICE is (c) 6 units

To EXPLAIN: Distance between A (-1, -1) and B (-1, 3) = \( \sqrt {(x_2-x_1)^2 + (y_2-y_1)^2} \)

= \( \sqrt {(-1 + 1)^2 + (3 + 1)^2} \)

= \( \sqrt {4^2} \)

= √16

= 4

Distance between B (-1, 3) and C(2, -1) = \( \sqrt {(x_2-x_1)^2 + (y_2-y_1)^2} \)

= \( \sqrt {(2 + 1)^2 + (-1-3)^2} \)

= \( \sqrt {3^2 + (-4)^2} \)

= \( \sqrt {9 + 16} \)

= 5

Distance between A (-1, -1) and C (2, -1) = \( \sqrt {(x_2-x_1)^2 + (y_2-y_1)^2} \)

= \( \sqrt {(2 + 1)^2 + (-1 + 1)^2} \)

= \( \sqrt {3^2 + 0^2} \)

= 3

Now, AC^2 + AB^2 = 4^2 + 3^2 = 16 + 9 = 25

BC^2 = 5^2 = 25

Hence, it is a right-angled triangle, right-angled at A.

Area of triangle = \( \FRAC {1}{2}\) × base × height = \( \frac {1}{2}\) × 4 × 3 = 6 units

28.

The point on x-axis which is at a distance 12 unit from the point (4, 6) is ___________(a) (-4 + \( \sqrt {11i} \), 0), (-4 – \( \sqrt {11i} \), 0)(b) (-4 – \( \sqrt {11i} \), 0), (4 – \( \sqrt {11i} \), 0)(c) (4 – \( \sqrt {11i} \), 0), (4 – \( \sqrt {11i} \), 0)(d) (4 + \( \sqrt {11i} \), 0), (4 – \( \sqrt {11i} \), 0)The question was posed to me by my college professor while I was bunking the class.The doubt is from Geometry in division Coordinate Geometry of Mathematics – Class 10

Answer»

The correct answer is (d) (4 + \( \SQRT {11I} \), 0), (4 – \( \sqrt {11i} \), 0)

For explanation I would say: Let the POINT on x-axis be (x, 0)

Distance between (4, 6) and (x, 0) = \( \sqrt {(x_2-x_1)^2 + (y_2-y_1)^2} \)

= \( \sqrt {(x-4)^2 + (0-6)^2} \)

= \( \sqrt {x^2-8x + 16 + 36} \)

= \( \sqrt {x^2-8x + 52} \)

The distance between (4, 6) and (x, 0) is 12

∴ \( \sqrt {x^2-8x + 52} \) = 12

Squaring on both sides, we get,

x^2 – 8x + 52 = 25

x^2 – 8x + 27 = 0

x = 4 + \( \sqrt {11i} \), 4 – \( \sqrt {11i} \)

29.

Three points A (x1, y1), B (x2, y2) and C (x3, y3) are collinear only when \(\frac {1}{2}\) {x1 (y2 – y3 ) + x2 (y3 – y1 ) + x3 (y1 – y2 ) } = 0.(a) False(b) TrueThe question was asked in a national level competition.The above asked question is from Geometry in portion Coordinate Geometry of Mathematics – Class 10

Answer»

The correct answer is (b) True

Easiest explanation: Consider three points (-3, 3), (-1, 2) and (1, 1)

We know that, area of triangle = \(\frac {1}{2}\){x1 (y2 – y3 ) + x2 (y3 – y1 ) + x3 (y1 – y2)}

The area of triangle = \(\frac {1}{2}\) {-3(2 – 1) + (-1)(1 – 3) + 1(3 – 2)} = \(\frac {1}{2}\) {-3 – 1 + 3 + 3 – 2} = \(\frac {0}{2}\) = 0

Hence if the points are collinear the area of triangle is zero.

30.

If A (x1, y1), B (x2, y2) and C (x3, y3) are the vertices of a triangle ABC, then its area is given by \(\frac {1}{2}\) {x1 (y2 – y3 ) + x2 (y3 – y1 ) + x3 (y1 – y2 ) }(a) True(b) FalseThe question was posed to me in an interview for internship.Query is from Geometry topic in portion Coordinate Geometry of Mathematics – Class 10

Answer»

Correct answer is (a) True

Explanation: A (x1, y1), B (x2, y2) and C (x3, y3) are the vertices of a triangle ABC.

Draw AL, CM, BN perpendicular to x – axis.

Then, ML = (x1 – x2), LN = (x3 – x1) and MN = (x3 – x2).

AREA of ∆ABC = AR(trap.BMLA) + ar(trap.ALNC) + ar(trap.BMNC)

 = {\(\frac {1}{2}\) (AL + BM) × ML} + {\(\frac {1}{2}\) (AL + CN) × LN} – {\(\frac {1}{2}\) (CN + BM) × MN}

 = {\(\frac {1}{2}\) (y1 + y2 ) × (x1 – x2)} + {\(\frac {1}{2}\) (y1 + y3 ) × (x3 – x1)} – {\(\frac {1}{2}\) (y2 + y3 ) × (x3 – x2)}

 = \(\frac {1}{2}\) {x1 (y1 + y2 – y1 – y3 ) + x2 (y2 + y3 – y1 – y2 ) – x3 (y1 + y3 – y2 – y3 ) }

 = \(\frac {1}{2}\) {x1 (y2 – y3 ) + x2 (y3 – y1 ) + x3 (y1 – y2 ) }

31.

What will be ratio in which the line 3x + y – 11 = 0 divides the line segment joining the points (0, -1) and (-3, -4)?(a) 1:2 (internally)(b) 1:2 (externally)(c) 2:1 (externally)(d) 2:1 (internally)I had been asked this question by my school principal while I was bunking the class.This is a very interesting question from Geometry in division Coordinate Geometry of Mathematics – Class 10

Answer»

Correct choice is (b) 1:2 (externally)

The EXPLANATION is: Let the RATIO in which the line 3x + y – 11 = 0 divides the line segment joining the points (0, -1) and (-3, -4) be k:1.

Using, section formula x = \(\frac {mx_2+nx_1}{m+n}\) and y = \(\frac {my_2+ny_1}{m+n}\)

The points are A(0, -1) and B(-3, -4) and the ratio is k:1.

∴ x = \(\frac {k(-3)+1(0)}{k+1} = \frac {-3k}{k+1}\)

y = \(\frac {k(-4)+1(-1)}{k+1} = \frac {-4k-1}{k+1}\)

Since, the point \((\frac {-3k}{k+1}, \frac {-4k-1}{k+1} )\) lies on the line 3x+y-11 = 0.

3 \((\frac {-3k}{k+1} + \frac {-4k-1}{k+1} )\)-11 = 0

3(-3k) + (-4k – 1) – 11(k + 1) = 0

-9k – 4k – 1 – 11K – 11 = 0

-24k – 12 = 0

-24k = 12

k = \(\frac {12}{-24} = \frac {-1}{2}\)

The ratio is 1:2 (externally).

32.

The coordinates of the ends of the diameter AB of a circle are A (-4, 7) and B(4, 7). What will be the coordinates of the center of the circle?(a) (0, -8)(b) (0, 8)(c) (0, 7)(d) (0, -7)I have been asked this question in a national level competition.This key question is from Geometry topic in portion Coordinate Geometry of Mathematics – Class 10

Answer» CORRECT ANSWER is (C) (0, 7)

Easiest explanation: We know that the diameter is TWICE the radius.

Hence, the center is the midpoint of the diameter.

Using, section formula x = \(\frac {mx_2+nx_1}{m+n}\) and y = \(\frac {my_2+ny_1}{m+n}\)

The points are A(-4, 7) and B(4, 7) and the RATIO is 1:1

∴ x = \(\frac {1(-4)+1(4)}{2} = \frac {0}{2}\) = 0

y = \(\frac {1(7)+1(7)}{2} = \frac {7+7}{2} = \frac {14}{2}\) = 7

Hence, the point is (0, 7).
33.

If A(0, 3), B(5, 0) and C(-5, 0) are the vertices of ∆ABC, then the triangle is __________(a) Right-angled(b) Isosceles(c) Scalene(d) EquilateralI had been asked this question in final exam.The doubt is from Geometry in division Coordinate Geometry of Mathematics – Class 10

Answer»

Right answer is (B) Isosceles

The explanation is: Distance between (0, 3) and (5, 0) = \( \SQRT {(x_2-x_1)^2 + (y_2-y_1)^2} \)

= \( \sqrt {(5-0)^2 + (0-3)^2} \)

= \( \sqrt {5^2 + -3^2 } \)

= \( \sqrt {25 + 9} \)

= √34

Distance between (5, 0) and (-5, 0) = \( \sqrt {(x_2-x_1)^2 + (y_2-y_1)^2} \)

= \( \sqrt {(-5-5)^2 + (0-0)^2} \)

= \( \sqrt {-10^2} \)

= 10

Distance between (0, 3) and (-5, 0) = \( \sqrt {(x_2-x_1)^2 + (y_2-y_1)^2} \)

= \( \sqrt {(-5-0)^2 + (0-3)^2} \)

= \( \sqrt {-5^2 + (-3)^2} \)

= \( \sqrt {25 + 9} \)

= √34

Since, the TWO sides of the triangle are equal.

Hence, the triangle will be isosceles triangle.

34.

If the point P(a, b) is equidistant from the points (3, 1) and (2, 0) then ____________(a) a + b = -3(b) a – b = -3(c) a + b = 3(d) a – b = 3I have been asked this question in an interview for job.This intriguing question originated from Geometry topic in portion Coordinate Geometry of Mathematics – Class 10

Answer»

Right answer is (a) a + b = -3

Easy explanation: The point is (a, b)

Distance between (3, 1) and (a, b) = \( \sqrt {(x_2-x_1)^2 + (y_2-y_1)^2} \)

= \( \sqrt {(a-3)^2 + (b-1)^2} \)

= \( \sqrt {a^2-6a + 9 + b^2-2b + 1} \)

= \( \sqrt {a^2-6a + 10 + b^2-2b} \)

Distance between (2, 0) and (a, b) = \( \sqrt {(x_2-x_1)^2 + (y_2-y_1)^2} \)

= \( \sqrt {(a-2)^2 + (b-0)^2} \)

= \( \sqrt {a^2-4a + 4 + b^2 } \)

Since, the point (a, b) is equidistant from (-1, 0) and (3, 9)

The distances will be equal

∴ \( \sqrt {a^2-6a + 10 + b^2-2b} = \sqrt {a^2-4a + 4 + b^2 } \)

SQUARING on both SIDES we get,

a^2 – 6a + 10 + b^2 – 2b = a^2 – 4a + 4 + b^2

-6a + 10 – 2b = -4a + 4

-2a – 6 = 2b

-a – b = 3

a + b = -3

35.

The coordinates of one end of the diameter AB of a circle are A (-2, -3) and the coordinates of diameter are (-2, 0). What will be the coordinates of B?(a) (2, -3)(b) (-2, 3)(c) (2, 3)(d) (-2, -3)This question was addressed to me during an interview for a job.Query is from Geometry in chapter Coordinate Geometry of Mathematics – Class 10

Answer»

Right choice is (b) (-2, 3)

For explanation I would say: We know that the diameter is twice the radius.

Hence, the CENTER is the midpoint of the diameter.

Using, section FORMULA x = \(\FRAC {mx_2+nx_1}{m+n}\) and y = \(\frac {my_2+ny_1}{m+n}\)

The points are A(-2, -3) and center is (-2, 0) and the ratio is 1:1

Let the coordinates of other side of the radius be (x, y).

∴ -2 = \(\frac {1(-2)+1(x)}{2} = \frac {-2+x}{2}\)

-4 = -2 + x

-4 + 2 = x

x = -2

0 = \(\frac {1(-3)+1(y)}{2} = \frac {-3+y}{2}\)

0 = -3 + y

y = 3

Hence, the point is (-2, 3).