Explore topic-wise InterviewSolutions in Current Affairs.

This section includes 7 InterviewSolutions, each offering curated multiple-choice questions to sharpen your Current Affairs knowledge and support exam preparation. Choose a topic below to get started.

1.

Solve the following differential equations. (dy)/(dx)=(4x+6y+5)/(3y+2x+4)

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ANSWER :2X - y +K
2.

Evaluate the following determinants. [[-6,0,0],[3,-5,7],[2,8,11]]

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SOLUTION :`[[-6,0,0],[3,-5,7],[2,8,11]]`
`(-6)[[-5,7],[8,11]]`=(-6)(-55-56)
(-6)(-111)=666
3.

If the system of equations : 2x+3y-z=0,3x+2y+kz=0,4x+y+z=0 have a set of non-zero integral solutions then,find the smallest positive value of z

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ANSWER :5
4.

Pentagons have 5 diagonals, as illustrated below. How many diagonals does the octagon below have?

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8
16
20
30

Answer :C
5.

Draw the graph of y=2cosx + sin2x

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Solution :We have `y=f(X) = 2cosx+ sin2x`
Clearly, DOMAIN of the function is R.
Also `f(x)` is periodic with period `2PI`.
So we NEED to draw the graph for the interval for the interval `[0,2pi]`.
`f(0) =0`
`f(x)=0`
`therefore 2cosx+2sincosx=0`
`therefore 2cosx(1+sinx)=0`
`therefore cosx=0` or `sinx=-1`
`therefore x=pi//2` or `x=(3pi)//2`
`f^(')(x) = -2sinx+2cosx2x`
`=-2(2sin^(2)x+sinx-1)`
`=-2(2sinx-1)(sinx+1)`
`f^(')(x) =0`
`therefore sinx=1//2` or `sinx=-1`
`therefore x=pi//6, (5pi)/6` or `x=(3pi)/2`
`f(pi//6) = 2cos(pi//6) + sin(pi//3)`
`=(3sqrt(3))/2`
`f(5pi//6) = 2cos(5pi//6+sin(5pi//3))`
`=-3sqrt(3)/2`
`f(3pi//2)=0`
So important points on graph paper as shown in the following figure.

From the points A to B, f(x) increases, from points B to D, f(x) decreases intersecting the x-axis at C, from points D to F, f(x) increases intersecting the x-axis at E.
Further `f^('')(x)=-2 cosx-4sin2x`
`f^('')(x) =0`at `x=(3pi//2)`, hence it is the point of inflection.
Since functions have period `2pi`, the graph of`y=f(x)` for `x in R` is as shown in the following figure.
6.

Let f(x) be a quadratic expression such that f(x) lt 0 AA x in R . If g(x)f'(x) + f''(x)then for x in R.

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`g(x) LT 0`
`g(x) LE 0`
`g(x) gt 0`
`g(x) GE 0`

ANSWER :A
7.

Evaluate the following integrals int x " tanh"^(-1)xdx, |x| lt1

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Answer :`(x^(2))/(2)TANH^(-1)x-(1)/(4)LOG|(1+x)/(1-x)|+(x)/(2)+c`
8.

IF bar(a)=2bar(i)+5bar(j)+bar(k),bar(b)=4bar(i)+mbar(j)+nbar(k)are collinear vectors then find m+n

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ANSWER :N = 2
9.

Fill in the gaps with correct answer choosing from the brackets.The correct expression is _____.(sin 1^0 > sin1,sin1^0 < sin1, sin1^0 =sin1)

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SOLUTION :`SIN1^@ < sin1^@`
10.

How many positive integers less than 1000 have the property that the sum of the digits of each such number is divisible by 7 and the number itself is divisible by 3?

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ANSWER :28
11.

If A,B and C are angles of a triangle, then the determinant |{:(-1,cosC,cosB),(cosC,-1,cosA),(cosB,cosA,-1):}| is equal to"........."

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0
-1
1
None of these

ANSWER :A
12.

State true or False .The planes 2x +4y -z + 1 = 0 and x - 2y - 6z + 3 = 0 are perpendicular to each other.

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ANSWER :T
13.

Evaluate the determinants in Exercises 1 and 2.{:|( 2,4),( -5,-1) |:}

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ANSWER :` 18`
14.

Match the points on the curve 2y^2=x+1 with the slope of normals at those points {:("I.",(7,2),"a",-4sqrt2),("II".,(0.1//sqrt2),b,-8),("III.",(1,-1),c,4),("IV.",(3,sqrt2),d,0),("","",e,-2sqrt2):}

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B,d,C,a
b,E,c,a
b,c,c,a
b,e,a,c

Answer :B
15.

If Delta_r= |[2r-1, mC_r,1],[m^2-1,2^m,m+1],[m^2+m+1,2^m+1,m+2]|, then sum_(r=0)^m Delta_r=

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0
`m^2-1`
`2^m(m^2-1)`
`2^(m-1)`

ANSWER :A
16.

The median of 100 observation grouped in classes of equal width is 55 if the median class is 50-60 and the number of observation less than 50 is 45, then frequency of the median class is _______

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ANSWER :`10`
17.

By vector method prove that the angle in a semi circle is a right angle.

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ANSWER :`/_APB=90^(@)`
18.

If a and b are two unit vectors inclined to X-axis at angles 30^(@) and 120^(@), then |a+b| is equal to

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`SQRT((2)/(3))`
`sqrt2`
`SQRT3`
2

Solution :Clearly, angle between a and `b=pi/2`
`implies a.b=0`
`:. |a+b|^(2)=a^(2)+b^(2)+2a.b=1+1+0=2`
`implies |a+b|=sqrt(2)`
19.

If x+ky-5=0 is a tangent to the ellipse 4x^(2)+9y^(2)=20 then k =

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3
`-3`
`PM3`
`PM4`

ANSWER :C
20.

Integrate the following functions : intx(4+x)^(1/4)dx

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ANSWER :`(4)/(9)(4+x)^(9/4)-(16)/(5)(4+x)^(5/4)+c`
21.

For each of the exercises given below, verify that thegiven function (implicit orexplicit) is a solution of the correspondingdifferential equation. (i) xy = ae^(x) + be^(-x) + x^(2) : x (d^(2)y)/(dx^(2)) + 2(dy)/(dx) - xy + x^(2) - 2 = 0 (ii) y = e^(x)(a cos x + b sin x) : (d^(2)y)/(dx^(2))- 2(dy)/(dx) + 2y = 0 (iii) y = x sin 3x : (d^(2)y)/(dx^(2)) + 9y - 6 cos 3x = 0 (iv) x^(2) = 2y^(2) log y : (x^(2) + y^(2)(dy)/(dx) - xy = 0

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22.

If each of the obsservationsx_(1) , x_(2) …..x_(n)is o increased by k , is a positive or negative number , then show that the variance ramains unchanged .

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ANSWER :`SIGMA _(2)^(1)`
23.

If A=[{:(1,0,2),(0,2,1),(2,0,3):}]then , prove that A^(3)-6A^(2)+7A+2I=O.

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ANSWER :`[{:(0,0,0),(0,0,0),(0,0,0):}]=O=R.H.S`.
24.

Find the number of ways of selecting cricket eleven from 20 players such that at least one of Sachin and Dravid must be excluded

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Answer :`""^(20)C_(11)-""^(18)C_(9)`
25.

The value of int_(-(pi)/(2))^((pi)/(2)) sqrt((1-cos 2x)/(2x)) dxis

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`(1)/(2)`
2
0
1

Answer :2
26.

Find a vector of magnitude sqrt(51) and makes equal angle with the vectors vec(a)=(1)/(3)(hati-2hatj+2hatk),vec(b)=(1)/(5)(-4hati-3hatk) and vec( c )=hatj.

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ANSWER :`+-(5hati+hatj-5hatk)`
27.

If the coefficients of rth and (r+1)th terms in the expansion of (1+x)^(24) are in the ratio 12 : 13, then r is the root of the quadratic equation

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`x^(2) - 5x + 6 = 0`
`x^(2) - 11x + 30 = 0`
`x^(2) - 14x + 13 = 0`
`x^(2) - 14x + 24 = 0`

Answer :D
28.

If a=1,+x+x^2... and b=1+y+y^2+...[x|lt1and]y|lt1, then prove that 1-xy+x^2y^2+x^3y^3+....=(ab)/(a+b-1)

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Solution :`a=1+x+x^2+...=1/(1-x)IMPLIES(1-x)=1 implies a-1=ax implies=(a-1)/a similarly,y=(B-1)/b`
`therefore1+xy+x^2y^2+....=1/(1-xy)=1/((a-1)(b-1))/1-(AB)=(ab)/(ab-(ab-a-b+1))=(ab)/(a+b-1)`
29.

If a random variable X has a binomial distribution B (8,1/2) then find X for which the outcome is the most likely.

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SOLUTION :GIVEN binomial distribution is B `(8.1/2)`
THUS n=8,p=`1/2,q=1/2`
We shall find X which is most likely i.e.for which p(x-r) is maximum where r=0,1,2,.......,8
As p=q, the probability is maximum when `^8C_r` is maximum
But `^8C_r`,r=0,1,2,....... 8 is maximum when r=4.
Thus the most likely OUTCOME is x=4.
30.

Find the number of ways of arranging 7 gents and 4 ladies around a circular table if no two ladies wish to sit together.

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ANSWER :`6!XX""^7P_4`
31.

The solution of (x^(2) + 1) (dy)/(dx) + 4xy = (1)/(x^(2) + 1) is

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ANSWER :x+c
32.

Three persons A, B and C, fire at a target in turn starting with A. Their probability of hitting the target are 0.4, 0.3 and 0.2 respectively. The probability of two hits is …………

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0.024
0.188
0.336
0.452

Answer :B
33.

Find the rank of the following matrices by row reduction method.[[3,-8,5,2],[2,-5,1,4],[-1,2,3,-2]]

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ANSWER :`RHO (C ) = 3`
34.

If Q is the image of the point P(2,3,4)under the reflection in the plane x-2y+5z =6 , then the equation of the line PQ is

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`(x-2)/(-1)=(y-3)/2=(z-4)/5`
`(x-2)/(1)=(y-3)/(-2)=(z-4)/5`
`(x-2)/(-1)=(y-3)/(-2)=(z-4)/5`
`(x-2)/(1)=(y-3)/(2)=(z-4)/5`

ANSWER :B
35.

Construct truth tables for the following and indicate which of these are tautologiesp^^(porq)rarr q.

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SOLUTION :
36.

Consider the binary operations ** R xx R rarrR and o : RxxR rarrR defined as a**b |a-b| and " a o b " = a, AA a , b in R . Show that ** is commutative but not associative , o is associative but not commutative. Further, show that AA a , b ,c in R , a ** ("b o c")= (a**b) o (a**c) . [If it is so , we say that the operation ** distributes over the operation o] . Does o distribute over ** ? Justify your answer.

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SOLUTION :N/A
37.

If in a triangleABC, r_1=2r_2=3r_3, then b : c =

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`4 : 3`
`5 : 4`
`2 : 1`
`3 : 2`

Answer :A
38.

Form the differential equation representing the given family of curves y= asin(x+b) where a,b are arbitrary constants.

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ANSWER :`(d^(2)y)/(DX^(2))+y=0`
39.

If x = alpha, y = beta, z = gamma is the solution, for the system of equations 2x - y + 8z = 13 3x + 4y + 5z = 18 5x - 2y + 7z = 20 then alpha beta + beta gamma + gamma alpha =

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1
0
7
`-3`

ANSWER :C
40.

The volume of a cube is increasing at the rate of 8 cm^(3) /s. How fast is the surface area increasing when the length of an edge is 12 cm?

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ANSWER :`8 PI CM^(2)//cm`
41.

Find the domains of defination of the following functions: (a) f(x)=sqrt(x^(3)-x^(2)), (b f(x)=sqrt(sin sqrtx) (c) fx)=sqrt(-sin^(2) pix), (d) f(x)=(1)/sqrt(|x|-x|) and g(x)=1/sqrt(x-|x|) (e) f(x)=arc sin (|x|x-3), (f) f(x)=arc cos ""1/(sin x)

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Answer :(a) `(1, +oo); (B) (2npi)^(2) LE x le (2n+1)^(2) PI^(2) (n=0,1,2,.....)`
(c) `x=0, PM 1, +2,.....; (d) (-oo,0)` (e) `[-4,2] or [2,4]`
`(f) x=(2n+1) pi/2 (n=0, pm1, PM2,...)`
42.

Prove thatsum_(k=0)^(n) (-1)^(k).""^(3n)C_(k)= (-1)^(n). ""^(3n-1)C_(n)

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Solution :Wehave,
`S = underset(k = 0)OVERSET(N)sum(-1)^(k) . .^(3n)C_(k) = .^(3n)C_(0) - .^(3n)C_(1) + .^(3n)C_(2) + "……" + (-1)^(n)..^(3n)C_(n)`
But
`.^(3n)C_(0) = .^(3n-1)C_(0)`
`-.^(3n)C_(1) = -.^(3n-1)C_(0) - .^(3n-1)C_(1)`
`.^(3n)C_(2) = .^(3n-1)C_(1).^(3n-1)C_(2)`
`-.^(3n)C_(3) = -.^(3n-1)C_(2) - .^(3n-1)C_(3)`
`{:("......"),("......"):}""{:("......"),("......"):}`
`(-1)^(n)..^(3n)C_(n) = (-1)^(n).^(3n-1)C_(n-1)+(-1)^(n).^(3n-1)C_(n)`
On adding, we GET
`S = (-1)^(n).^(3n-1)C_(n)`.
43.

Let X ={x,y} and Y ={u,v}. Write down all the functions that can be defined from X To Y. How many of these are (i) one-one (ii) onto and (iii)one-one and onto ?

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Solution :The function from X={x,y} to y ={u,v} are :`f_1 ={(x,u),(y,v)}`
`f_2={(x,v),(y,u)}`
`f_3 ={(x,4),(y,u)`
`f_4={(x,v),(y,v)}`
Out of these 4 FUNCTIONS there are :(i) 2 one-one functions
(ii) 2 ONTO functions
(III) 2 one-one and onto fuction.
44.

Consider the unction f(x)=int_(0)^(x)(5ln(1+t^(2))-10t tan^(-1)t+16sint)dt Which is not true for int_(0)^(x)f(t)dt gt?

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POSITIVE for all `x in (0,1)`
increasing for all `x in (0,1)`
non-monotonic for all `x in (0,1)`
NONE of these

Solution :`f(x)=int_(0)^(x)(5ln(1+t^(2))-10t tan^(-1)t+16sint)dt.`
`rArr""f'(x)=5ln(1+x^(2))-10x tan^(-1)x+16 SINX`
`rArr""f''(x)=2(8 cos x-5 tan^(-1)x)`
`rArr""f''(x)=-2(8sinx+(5)/(1+x^(2)))lt0AAx in (0,1)`
So, f''(x) is decreasing `AA x in (0,1)`
`rArr""f''(x)gtf''(1)=2(8cos1-(5pi)/(4))`
`""gt2(8cos.(pi)/(3)-(5pi)/(4))`
`""=2(4-(5pi)/(4))gt0`
So, f''(x) is increasing, for `x gt 0 , f'(x)gtf'(0)=0`
So, f(x) is increasing, for `x gt0, f(x) gt f(0)=0`
So, `int_(0)^(x)f(t)` is positive and increasing.
45.

int(x^(2))/((x^(2)+a^(2))(x^(2)+b^(2)))dx

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`(1)/((a^(2)-b^(2)))[(1)/(b)tan^(-1)((x)/(b))-(1)/(a)"tan"^(-1)((x)/(a))]+C`
`(1)/((b^(2)-a^(2)))[(1)/(b)tan^(-1)((x)/(b))-(1)/(a)"tan"^(-1)((x)/(a))]+c`
`(1)/(b)tan^(-1) ((x)/(b))-(1)/(a)tan^(-1)((x)/(a))+c`
`(1)/(a)tan^(-1) ((x)/(b))-(1)/(a)tan^(-1)((x)/(a))+c`

ANSWER :A
46.

The magnitude of the projection of vector (4, 1, 3) and (1, -2, 3) is …………….

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`(15)/(SQRT(14))`
`(15)/(14)`
`(11)/(14)`
`(11)/(sqrt(14))`

ANSWER :D
47.

Hannah is 5 years younger than Nora , who is x years old, Which of the following is an expression for Hannah's age in 2 years ?

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x-3
x+3
x+7
2x-3

Answer :A
48.

If f(x) is a function of x such that (1)/((1+x)(1+x^(2)))=(A)/(1+x)+(f(x))/((1+x^(2)) for all x in R then f(x) is

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`(1-x)/(2)`
`(1+x)/(2)`
`1-x`
`1+x`

ANSWER :A
49.

Consider the non-empty set consisting of children in a family and a relation R defined as aRb, if a is brother of b. Then, R is

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SYMMETRIC but not transitive
transitive but not symmetric
neither symmetric nor transitive
both symmetric and transitive

Answer :B
50.

Find the relationship between a and b so that the function f defined by f(x)={{:(ax+1," if "x le 3),(bx+3," if "x gt 3):} is continuous at x=3.

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ANSWER :`a=b + (2)/(3)`