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.

`20 ml` of an `H_2 O_2` solution on reaction with excess of acidified `KMnO_4` released `224` cc of `O_2`. What is the volume strength of that `H_2 O_2` ?A. 5.6 volB. 11.2 volC. 22.4 volD. 2.8 vol

Answer» Correct Answer - A
`2MnO_4^(-) + 5H_2 O_2 + 6H^+ rarr 2 Mn^(2+) + 5O_2 + 8 H_2O`
`22,400 "ml of" O_2 -= 34 g of H_2 O_2`
`224` ml of `O_2 -= 0.34 g of H_2 O_2`
Normality `= (0.34)/(17) xx (1000)/(20) = 1`
Volume strength `= (5.6) (N) = 5.6 Vol`.
2.

Choose the word from the options given to form a compound word with “drop”. (a) heave (b) mock (c) eaves (d) out

Answer»

Correct answer is (c) leaves

3.

Choose the word from the options given to form a compound word with “out” , (a) in (b) wipe(c) weather (d) hind

Answer»

Correct answer is (b) wipe

4.

There is no bread left because we ______ it all. A) have eaten B) has been eaten C) had eaten D) have been eaten

Answer»

Correct option is A) have eaten

5.

[" of "0],[CH_(3)-c-NH_(2)+H_(2)O]

Answer» Reduce Zero Numerator

`0 + 1 / 20`

Remove Adding Zero

`1 / 20`

*0.05*
6.

What are the optimum temperature and pH at which enzymes are highly active ?

Answer»

(Hint : Temperature 298-310 K and pH 5 to 7)

7.

The men were to ______ but the manager decided to give them a second change. A) have been dismissed B) dismissed C) being dismissed D) be dismissing

Answer»

Correct option is A) have been dismissed

8.

Name the enzyme which converts milk into curd.

Answer»

(Hint : Lactobacilli.)

9.

(i) \( \int_{0}^{\pi} \theta \sin ^{2} \theta \cos \theta d \theta \)

Answer»

\(\int_0^\pi \theta\,sin^2\theta\,cos\theta\,d\theta\)

\(\int_0^\pi \theta\,(1-cos^2\theta)\,cos\theta\,d\theta\) 

\(\int_0^\pi \theta\,cos\theta\,d\theta\) - \(\int_0^\pi \theta\,cos^3\theta\,d\theta\) 

\([\theta\int cos\theta\,d\theta]_0^{\pi}\) - \(\int_0^{\pi}(1.\int cos^3\theta\,d\theta)\)

\([\theta\,sin\theta]_0^{\pi}\) - \(\int_0^\pi \theta\,sin\theta\,d\theta\) - \([\theta(sin\theta - \frac{sin^3\theta}{3})]_0^{\pi}\) + \(\int_0^\pi(sin\theta - \frac{sin^3\theta}{3})d\theta\)

(∵\(\int cos^3\theta\,d\theta\) = \(\int (1-sin^2\theta)cos\theta\,d\theta\) 

\(\int cos\theta\,d\theta\) - \(\int sin^2\theta\,cos\theta\,d\theta\) 

= \(sin\theta-\frac{sin^3\theta}{3}\))

= (π sinπ - 0) + \([cos\theta]_0^{\pi}\) - (π(sinπ - \(\frac{sin^3\pi}{3}\)) - 0) - \([cos\theta]_0^{\pi}\) - \(\frac{2}{3}\)\(\int_0^{\pi/2} sin^3\theta\,d\theta\) 

= 0 - 0 - \(\frac{2}{3}\)\(\frac{\Gamma(\frac{3+1}{2})\Gamma(\frac{1}{2})}{2\Gamma(\frac{5}{2})}\) 

(\(\int_0^{\pi/2} sin^m\theta\,cos^n \theta d\theta\) = \(\frac{\Gamma(\frac{m+1}{2})\Gamma(\frac{n+1}{2})}{2\Gamma(\frac{m+n+1}{2})}\))

\(\frac{2}{3}\)\(\frac{\Gamma(2)\Gamma(\frac{1}{2})}{2.\frac{3}{2}.\frac{1}{2}\Gamma(\frac{1}{2})}\) 

(∵ \(\Gamma(n+1)=n\Gamma(n)\))

\(-\frac{2}{3}\times \frac{2}{3}\times 1!\) 

(\(\Gamma(2) = 1!=1\))

\(\frac{-4}{9}\).

10.

(ii) \( \int_{0}^{\pi} x \sin ^{6} x \cos ^{4} x d x \)

Answer»

Let I = \(\int\limits_0^\pi x\,sin^6x\,cos^4x\,dx\) ....(1)

∴ I = \(\int\limits_0^\pi (\pi -x)\,sin^6(\pi-x)\,cos^4(\pi-x)\,dx\) ....(2)

∴ 2I = \(\int\limits_0^\pi \pi\,sin^6x\,cos^4x\,dx\) (By adding (1) & (2))

⇒ I = \(\frac{\pi}{2}\int\limits_0^\pi\,sin^6x\,cos^4x\,dx\)

\(\frac{\pi}{2}\) x 2\(\int\limits_0^\pi\,sin^6x\,cos^4x\,dx\)

= π \(\frac{\Gamma(\frac{6+1}{2}).\Gamma(\frac{4+1}{2})}{2\Gamma(\frac{6+4+2}{2})}\)(By gamma function)

\(\frac{\pi}{2}\) \(\frac{\Gamma(\frac{7}{2}).\Gamma(\frac{5}{2})}{\Gamma(6)}\)

\(\frac{\pi}{2}\)\(\frac{\frac{5}{2}.\frac{3}{2}.\Gamma(\frac{1}{2})\times \frac{3}{2}.\frac{1}{2}.\Gamma(\frac{1}{2})}{5!}\) 

(\(\Gamma(n) = (n-1)!\) n ∈ N & \(\Gamma(n+1)=n\Gamma(n)\))

= \(\frac{\pi}{2}\) x \(\frac{45}{32}\) x \(\frac{1}{120}\) √π x √π (∵ \(\Gamma(\frac{1}{2})= \sqrt {\pi}\))

= \(\frac{3\pi^2}{512}\)

11.

Find the sum of `h+2e^(2)h+2e^(4)h+2e^(6)h +.....`

Answer» `h[1+2e^(2)(1+e^(2)+e^(4)+.....)]`
`=h[1+2e^(2)((1)/(1-e^(2)))]`
`=h((1+e^(2))/(1-e^(2)))`
12.

Solve `x^(2)+x-2=0`

Answer» For quadratic equation
` ax^(2)+bx +c=0`
`x=(-b+-sqrt(b^(2)-4ac))/(2a)`
So, for given equation ` x^(2)+x-2=0`
`x=(-1+-sqrt(1+8))/(2)=(-1+-3)/(2)=1,-2`
13.

Find the directional derivative of q = 4x3 - 3x2 * y2 (2.-1.1) along the line which makes equal angles with Co-ordinate axes.

Answer»

q =  4x3 - 3x2y2

\(\vec ∇q\) = (\(\hat i \frac{\delta}{\delta x}\) + \(\hat j \frac{\delta}{\delta y}\) + \(\hat k \frac{\delta}{\delta z}\))q

\(\hat i \frac{\delta}{\delta x}\)(4x3 - 3x2y2) + \(\frac{j\delta}{\delta y}\)(4x3 - 3x2y2) + \(0\hat k\)

\(\hat i\) (12x2 - 6xy2) + \(\hat j\)(-6x2y)

Direction cosines of line which makes equal angles with coordinate axis are (±\(\frac{1}{\sqrt 3}\), ±\(\frac{1}{\sqrt 3}\)\(\frac{1}{\sqrt 3}\)).

∴ Direction derivative of q in direction of line is

= (\(\vec ∇q\)).(\(\frac{1}{\sqrt3}\hat i\) + \(\frac{1}{\sqrt3}\hat j\) + \(\frac{1}{\sqrt3}\hat k\))

\(\hat i\) (\(12x^2-6xy^2\)) + \(\hat j\) (-6x2y)(\(\frac{1}{\sqrt3}\hat i\) + \(\frac{1}{\sqrt3}\hat j\) + \(\frac{1}{\sqrt3}\hat k\))

\(\frac{1}{\sqrt 3}\)\((12x^2-6xy^2)\) - \(\frac{6x^2y}{\sqrt 3}\) 

Direction derivative at (2,-1,1) = \(\frac{1}{\sqrt 3}\)(12 x 4 - 6 x 2 x 1) - \(\frac{6\times 2^2\times -1}{\sqrt 3}\) 

\(\frac{1}{\sqrt 3}\)(48 - 12) + \(\frac{24}{\sqrt 3}\) 

\(\frac{60}{\sqrt 3}\) 

= \(20\sqrt 3\).

14.

If \( y=x^{\tan x}+(\sin x)^{\cos x} \), Find \( \frac{d y}{d x} \)

Answer»

y = xtanx + (sinx)cosx

Let y1 = xtanx & y2 = (sinx)cosx

∴ \(\frac{dy}{dx}\) \(\frac{dy_1}{dx}\) + \(\frac{dy_2}{dx}\) .........(1)

Now,

logy1 = tanx loga & logy2 =  cosx log sinx

(∵ log ab = blog a)

∴ \(\frac{1}{y_1}\frac{dy_1}{dx}\) = \(\frac{tanx}{x}\) + sec2x logx

⇒ \(\frac{dy_1}{dx}\) = (\(\frac{tanx}{x}\) + sec2x logx) xtanx

\(\frac{1}{y_2}\frac{dy_2}{dx}\) = \(\frac{cosx}{sinx}\times cosx\) - sinx log sinx

⇒ \(\frac{dy_2}{dx}\) = (cosx cotx - sinx log sinx)(sinx)cosx

From (1),

\(\frac{dy}{dx}\) =  (\(\frac{tanx}{x}\) + sec2x logx) xtanx + (cosx cotx - sinx log sinx)(sinx)cosx

15.

Simplify: \(\frac1{3-\sqrt8}-\frac1{\sqrt8-\sqrt7}+\frac1{\sqrt7-\sqrt6}\)\(-\frac1{\sqrt6-\sqrt5}+\frac1{\sqrt5-2}\) 

Answer»

\(\frac1{3-\sqrt8}-\frac1{\sqrt8-\sqrt7}+\frac1{\sqrt7-\sqrt6}\)\(-\frac1{\sqrt6-\sqrt5}+\frac1{\sqrt5-2}\) 

\(= \frac{3+\sqrt8}{9-8}-\frac{\sqrt8+\sqrt7}{8-7}+\frac{\sqrt7+\sqrt6}{7-6}\)\(-\frac{\sqrt6+\sqrt5}{6-5}+\frac{\sqrt5+2}{5-4}\)

= (3 + √8) - (√8 + √7) + (√7 + √6) - (√6 - √5) + (√5 + 2)

 = 3 + 2 = 5

16.

Write four numbers which are divisible by 6 but not by 12.

Answer»

Multiples of 6 are 6,12,18,24,30,36,42,48,54,60,66………………………

Multiples of 12 are 12,24,36,48,60,72,84,96,108,120,132………………..

Here 6,18,30,42,54,66………… are not multiples of 12.

So if a number is divisible by 6,it is not always divisible by 12.

17.

Subtract:4x by x2 - 1 - x + 1 by x - 1.

Answer»

\(\frac{4x}{x^2-1}-\frac{x+1}{x-1}\)

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

\(=\frac{4x-(x^2+2x+1)}{x^2-1}\) 

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

\(=-\frac{x^2-2x+1}{x^2-1}\) 

\(=-\frac{(x-1)^2}{x^2-1}\) 

\(=\frac{(x-1)^2}{1-x^2}\)

18.

Smallest prime number

Answer»

2 is the smallest prime number. 

19.

Given, `y=sin 2x` . Then find `(dy)/(dx)` .

Answer» `(dy)/(dx)=(d)/(dx) (sin 2x)`
`=(d(sin u))/(du)xx(du)/(dx)`
Here , u=2x
`:. " " (du)/(dx)=(d(2x))/(dx)=2 "and " (d(sin u))/(du)=cos u`
`:. " " (dy)/(dx) =cos u xx2 `
`=2 cos 2x `
Or
`(dy)/(dx)=(d)/(dx)(sin 2x)`
`=(d)/(d(2x)) sin (2x) xx (d(2x))/(dx)`
` cos 2x xx 2 = cos 2x`
20.

 Solve: x4 - 13x2 + 42 = 0

Answer»

x4 - 13x2 + 42 = 0

x4 - 7x2 - 6x2 + 42 = 0

⇒ x2(x2 - 7) - 6(x2 - 7) = 0

⇒ (x2 - 7) (x2 - 6) = 0

⇒ (x2 - 7) = 0 or x2 - 6 = 0

⇒ x = \(\pm\sqrt7\) or x = \(\pm\sqrt6\) 

Hence, roots or given equation are -√6, √6, -√7 & √7.

21.

7. The length of a field is 10 meter more than the breadth of the field. If perimeter of the field is 100 \( m \), find the dimensions of the field.

Answer»
please answer here 

22.

Given, `y=(ax+b)^(2)` , evaluate ` (dy)/(dx)`.

Answer» Method I :
Substituting (ax+b)=u
Then `" "(du)/(dx)=(d(ax+b))/(dx)=a`
and `" "(dy)/(du)=(d(ax+b)^(2))/(du)=(d(u)^(2))/(du)=2u`
`:. " " (dy)/(dx)=(dy)/(du) xx (du)/(dx)=2u xx a =2 (ax+b)a`
`" " =2a(ax+b)`
Method II :
`y=(ax+b)^(2)`
`=a^(2)x^(2)+b^(2)+2abx`
`"Then" " " (dy)/(dx)=(d)/(dx)[a^(2)x^(2)+b^(2) + 2abx]`
`=(d)/(dx) (a^(2)x^(2))+(d)/(dx)(b^(2)) +(d)/(dx) (2abx)`
`=a^(2)=(d(x)^(2))/(dx)+ 0+ 2ab(dx)/(dx)`
`=a^(2)xx2x+2ab xx1`
`=2a(ax+b)`
23.

)42) If \( \alpha \) and \( \beta \) are the roots of the equation \( x^{2}+x-4=0 \) form the quadratic equation whose roots are \( \alpha^{2} \) and \( \beta^{2} \).

Answer»
given-:

a+b=-1............ eqn ¹
ab=-4. ............. eqn ²

on squaring eqn ¹
a²+b²+2ab=1
a²+b²=9

on squaring eqn ²
a²b²=16

hence the eqn is
x²+9x+16=0

♥ 
24.

PBA and PDC are two secants. AD is the diameter of the circle with center at O. ∠A = 40°, ∠P = 20°. Find the measure of ∠DBC.(a) 30° (b) 45° (c) 50° (d) 40°

Answer»

Answer : (a) 30º 

In ∆ ADP, ext. ∠ADC = Int. ∠s (∠A + ∠P) 

= 40° + 20° = 60°. 

∠ABC = ∠ADC = 60° (Angles in the same segment)

\(\because\) AD is the diameter, ∠ABD = 90°

∴  ∠DBC = ∠ABD – ∠ABC = 90° – 60° 

= 30°

25.

If tanA = \(\frac{3}{4}\), find the value of \(\frac{1}{sinA}+\frac{1}{cosA}\)

Answer»

tanA = \(\frac{3}{4}\) = \(\frac{3k}{4k}\)

sinA = \(\frac{3k}{5k}\) = \(\frac{3}{5}\), cosA = \(\frac{4k}{5k}\) = \(\frac{4}{5}\)

\(\frac{1}{sinA}+\frac{1}{cosA}\)

= \(\frac{5}{3}+\frac{5}{4}\)

\(\frac{(20+15)}{12}\)

\(\frac{35}{12}\)

26.

40) Find the square root of: \( \left(6 x^{2}+x-1\right)\left(3 x^{2}+2 x-1\right)\left(2 x^{2}+3 x+1\right) \)

Answer»

Let f(x) = (6x2 + x - 1) (3x2 + 2x - 1) (2x2 + 3x +1)

= (3x-1)(2x+1)(3x-1)(x+1)(2x+1)(x+1)

= (3x+1)2(2x+1)2(x+1)2

∴ square roots f(x) is \(\sqrt{f(x)}\) = (3x-1)(2x+1)(x+1).

27.

39) Simplify: \( \frac{a^{2}-16}{a^{3}-8} \times \frac{2 a^{2}-3 a-2}{2 a^{2}+9 a+4} \div \frac{3 a^{2}-11 a-4}{a^{2}+2 a+4} \)

Answer»

\(\frac{a^2+6}{a^3-8}\) x \(\frac{2a^2-3a-2}{2a^2+9a+4}\) ÷ \(\frac{3a^2-11a-4}{a^2+2a+4}\)

\(\frac{(a+4)(a-4)}{(a-2)(a^2+2a+4)}\) x \(\frac{(2a+1)(a-2)}{(2a+1)(a+4)}\) x \(\frac{(a+2)^2}{(3a+1)(a-4)}\) 

\(\frac{(a+2)^2}{(a^2+2a+4)(3a+1)}\) 

28.

Find the area of a square,whose perimeter is 64 m.

Answer»

The perimeter of square is 4a=64
a=16
The area of square is a2 =16×16
=256cm2

29.

The age of sita and her sister are in the ratio of 3:8. after 12 years the ratio of their ages is 7:12. find there present ages.

Answer»

Let the age of Sita and her sister be 3x and 8x respectively. 

After 12 years, 

Sita's age = 3x + 12 and her sister's age = 8x + 12 

A/Q,

3x + 12 / 8x + 12 = 7 /12 

36x + 144 = 56x + 84 

60 = 20x 

x = 3, 

Sita's age = 3x = 9 years 

Sister's age = 8x = 24 years. 

Therefore, the ages of Sita and her sister are 9 and 24 years respectively.

30.

\( =\left(\frac{3}{5}\right)^{11} \div\left(\frac{3}{5}\right)^{6} \)

Answer»
= am ÷ an = am-n
= (3/5) 11-6
= (3/5)5
31.

38 If \( A=\frac{x}{x+1} B=\frac{1}{x+1} \) prove that \( \frac{(A+B) 2+(A-B) 2}{A \div B}=\frac{2(x 2+1)}{x(x+1) 2} \)

Answer»

We have,

A = \(\frac{x}{x+1}\),

B = \(\frac{1}{x+1}\)

\(\frac{(A+B)^2+(A-B)^2}{A\,÷\,B}\) = \(\frac{B[(A^2+B^2+2AB)+(A^2+B^2-2AB)]}{A}\)

\(\frac{2B(A^2+B^2)}{A}\) 

\(\frac{\frac{2}{x+1}((\frac{x}{x+1})^2+(\frac{1}{x+1})^2)}{\frac{x}{x+1}}\)

\(\frac{2}{x}\)\((\frac{x^2+1}{(x+1)^2})\) 

\(\frac{2(x^2+1)}{x(x+1)^2}\)

Hence proved.

32.

Find the area of each of the following triangles:(i)(ii)(iii)

Answer»
"QUESTION INCOMPLETE "
33.

A force F=(a+bx) acts on a particle in x direction where a and b are constants . Find the work done by this force during displacement from `x_(1)` to `x_(2)` .

Answer» Work done for displacement dx
`dW=Fdx=(a+bx)dx`
Total work done `W= int dW`
`=int_(x_(1))^(x_(2))(a+bx)dx`
`=[ax+(bx^(2))/(2)]_(x_(1))^(x_(2))`
` =a(x_(2)-x_(1))+(b)/(2)(x_(2)^(2) -x_(1)^(2))`
34.

Find value of `(104)^(1//2)` using binomial approx.

Answer» `(104)^(1//2)=(100 +4)^(1//2)=10 [ 1 + 0.04]^(1//2)`
` =10 [ 1+0.02]=10.2`
35.

Find a quadratic polynomial whose zeroes are 5 - 3√2 and 5 + 3√2.

Answer»

Sum of zeroes = 5 - 3√2 + 5 + 3√2 = 10 

Product of zeroes= (5 - 3√2)(5 + 3√2) = 7 

P(x)= x2 - 10x + 7

36.

Find the point on x-axis which is equidistant from the points (2,-2) and (-4,2)

Answer»

Let P(x,0) be a point on X-axis 

PA = PB 

PA2 = PB2 

(x - 2)2 + (0 + 2)2 = (x + 4)2 + (0 - 2)2 

x2 + 4 - 4x + 4

= x2 + 16 + 8x + 4 

-4x + 4 = 8x + 16 

x = -1 

P(-1,0)

37.

A ball of mass `m` inside a smooth spherical shell of radius `R` with velocity `sqrt(2qR)` at `A` What is the direction of force acting on the ball, when it reaches `B` ? A. BPB. BQC. BRD. BS

Answer» Correct Answer - A
38.

Find the square root of 21 – 2√54.1. 3√2 – √3   2. √2 – √3  3. 18 – 3√3  4. 9 – 3√3

Answer» Correct Answer - Option 1 : 3√2 – √3   

Given:

The number is 21 – 2√54

Formula Used:

(a + b)2 = a2 + b2 + 2 × a × b

Calculation:

The square root of 21 – 2√54

⇒ √(21 – 2√54)

⇒ √(21 – 2 × √18 × √3)

⇒ √(18 + 3 – 2 × √18 × √3)

⇒ √[(√18)2 + (√3)2 – 2 × √18 × √3]

⇒ √(√18 – √3)2

⇒ √18 – √3

⇒ 3√2 – √3

The square root of 21 – 2√54 is 3√2 – √3.

39.

The product of the two integers x and y where x > 65 and y > 80, is 5780 and their HCF is 17 then what is the sum of the two integers?1. 682. 853. 1534. 136

Answer» Correct Answer - Option 3 : 153

Given:

The product of the two number = 5780

HCF = 17

Concept used:

The HCF defines the greatest factor present in between two or more numbers.

Calculation:

Let the two number be 17x and 17y

The product of the two number = 5780

⇒ 17x × 17y = 5780

⇒ 289 xy = 5780

⇒ xy = 20

The possible value of x and y is (1, 20), (20, 1), (2, 10), (10, 2), (4, 5), (5, 4)

So the value which satisfied above condition is 4, 5

The first integer is 68 and the second integer is 85

Sum = 68 + 85 = 153

∴ The sum of the two integers is 153

40.

One is asked to say a two digit number. How many two digit numbers are there. What is the probability of one of the digit being 1. What is the probability of the product of the digits being a prime number.

Answer»

prime number=1/36 = 1/6

Hence, the required probability is 16.

41.

Debt equity ratio is a measure of

Answer»

Answer: Long term solvency

42.

 write the expression an-ak for the AP a, a+d,a+2d....hence find the d of the AP for which 25 term is 10 morethan the 23rd term ?????

Answer»
Actually this is not trigonometry question check question correctly 

43.

If x = cosθ, then find the value of (x6 + 1/x6)

Answer»

∵ x = cosθ + isinθ

⇒ x6 = (cos θ + isinθ)6 = cos6θ + isin6θ

⇒ 1/x6  = cos6θ – isin6θ

∴ x6 + 1/x6 = 2cos6θ

44.

The opposite angular points of a square are (5,4) and (-1,6). Find the coordinates of remaining two vertices.

Answer»

We know, 
properties of square : 
(1) all sides are equal 
(2) angle between two sides = 90° 

use this concept here, 
Let one unknown point of square is C(P, Q) given, A( 5, 4) , D(-1, 6) 

AC = DC 
AC² = DC² 
(P-5)² + (Q -4)² = (P+1)² + (Q -6)² 
-10P +25 -8Q + 16 = 2P +1 -12Q + 36 
-12P + 4Q + 4 = 0 
-3P + Q + 1 = 0 ________(1)

AC² + DC² = AD²
(P+1)² + (Q -6)² + (P-5)² + (Q -4)² = (6)² + (2)² 
2P² + 2Q² -8P -20Q + 78 = 40 
P² + Q² -4P - 10Q + 19 = 0-----------(2)
from (1) and (2) 

P² + (3P-1)² -4P -10(3P-1) + 19 = 0
10P² +1 - 6P -4P -30P +10 + 19 = 0
10P² - 40P + 30 = 0
P² -4P + 3 = 0
P = 1 and 3 
Q = 3P -1 = 2 and 8 
hence, 
two unknown points of square are 
( 1 , 2) and (3, 8)

45.

If f : R → R, g : R → R are defined by f(x) = 3x – 1, g(x) = x2 + 1, then find fog(2).

Answer»

Given f(x) = 3x –1 and g(x) = x2 +1 

(fog) (2) = f [g (2)] 

= f [22 + 1] = f (5) 

= 3 (5) – 1 

= 14 

∴ (fog) (2) = 14

46.

For what values of m, the equation x2 – 2(1 + 3m)x + 7(3 + 2m) = 0 will have equal roots?

Answer»

The given equation will have equal roots if its discriminant is 0.

Here ∆ =[(–2(1 + 3m)]2 – 4 (1) [7 + (3 + 2m)]

= 4(1 + 9m2 + 6m) – 28(3 + 2m)

= 9m2 – 8m – 20

= (m – 2) (9m + 10)

Hence ∆ =0 ⇔ m = 2, −10/9

47.

If two coins are tossed simultaneously. Find the probability of getting 2 heads.

Answer» P ( Two Head) `= (1)/(4)`
48.

Find the number of ways of arranging the letters of the word TRIANGLE so that the relative positions of the vowels and consonants are not disturbed.

Answer»

In a given, word, [Hint : Vowels – A, E, I, O U]

number of vowels is 3

number of consonants is 5

C C V V C C C V

Since the relative positions of the vowels and consonants are not disturbed, the 3 vowels can be arranged in their relative positions in 3! ways and the 5 consonants can be arranged in their relative positions in 5! ways.

∴ The number of required arrangements = (3!) (5!) = (6) (120) = 720.

49.

Find the inverse of the function f : R → R defined by f(x) = ax + b, (a ≠ 0), a, b ∈ R.

Answer»

Given f(x) = ax + b 

Let f(x) = y 

Then ax + b = y 

⇒ ax = y – b 

Since a ≠ 0 

⇒ x = y - b/a

⇒ f-1(y) = y - b/a

Hence f-1(x) = x - b/a

50.

Find the sum of the squares and the sum of the cubes of the roots of the equation x3 – px2 + qx – r = 0 in terms of p, q, r.

Answer»

Let α, β, γ be the roots of the given equation then

α + β + γ = p, αβ + βγ + γα = q,

αβγ = r

Sum of the squares of the roots is α2 + β2 + γ2

= (α + β + γ)2 – 2 (αβ + βγ + γα)

= p2 – 2q

Sum of the cubes of the roots is α3 + β3 + γ3

= (α + β + γ) (α2 + β2 + γ2 – αβ – βγ – γα) + 3αβγ

= p(p2 – 2q – q) + 3r

= p(p2 – 3q) + 3r