Quantitative Aptitude

General Questions

Quantitative Aptitude Exercise Mode

General Questions

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QUEST ? !
Question 11
If 4(x –y) = 64 and 4 (x + y) = 1024, then find the value of x.

A
3
B
1
C
6
D
4
Correct Answer: Option D

4 (x – y) = 64

4 (x – y) = 64 = 43

Equation 1) x – y = 3

4 (x + y) = 1024 = 45

Equation 2) x + y = 5

Solving equation (1) and (2), we get

x = 4 and y = 1

Crosscheck the answers by substituting the values of x and y in the given expression.

4 (4 – 1) = 43 = 64 and 4 (4 + 1) = 45 = 1024

Hence, the answers x = 4 and y = 1 are correct.

Question 12
If 9x – 9x – 1 = 648, then find the value of xx

A
4
B
9
C
27
D
64
Correct Answer: Option D

xm × xn = xm + n

9x – 9x – 1 = 648

9x – 1 (9 – 1) = 648

9x – 1 = (648/8) = 81

9x – 1 = 92

x – 1 = 2

x = 2 + 1 = 3

xx = 33 = 27

Alternate solution:

Select the given options and substitute the value of x = 5, 6, 1.5 and 3 in the given expression.

Substituting value of x = 3,

9x – 9x – 1 = ?

93 – 93 – 1 = 648

Value of x = 3

xx = 33 = 27

Question 13
If m and n are whole numbers such that mn = 121, the value of (m - 1)n + 1 is:

A
1
B
10
C
121
D
1000
Correct Answer: Option D

We know that 112 = 121.

Putting m = 11 and n = 2, we get:

(m - 1)n + 1 = (11 - 1)(2 + 1) = 103 = 1000.

Question 14
(17)3.5 x (17)? = 178

A
2.29
B
2.75
C
4.25
D
4.5
Correct Answer: Option D

Let (17)3.5 x (17)x = 178.

Then, (17)3.5 + x = 178.

 3.5 + x = 8

 x = (8 - 3.5)

 x = 4.5

Question 15
Find the value of : 


A
132
B
177
C
185
D
225
Correct Answer: Option B
Question 16
(243)n/5 x 32n + 1 = ?

9n x 3n - 1

A
1
B
2
C
9
D
3 n
Correct Answer: Option C

Given Expression
= (243)(n/5) x 32n + 1

9n x 3n - 1

= (35)(n/5) x 32n + 1

(32)n x 3n - 1

= (35 x (n/5) x 32n + 1)

(32n x 3n - 1)

= 3n x 32n + 1

32n x 3n - 1

= 3(n + 2n + 1)

3(2n + n - 1)

=

33n + 1

33n - 1

= 3(3n + 1 - 3n + 1)   = 32   = 9.

Question 17
(1331)– (2/3)  =  ?

A
-1/11
B
-11/121
C
1/121
D
121/11
Correct Answer: Option C

Cube root of 1331 is 11. Therefore,
 (113)– (2/3)

 Hint: 
 Remember the law of indices (xm)n = xmn

 (11) – 3 × (2/3) = 11–2


 Hint:  x-1  = 1/x

 

11-2  = 1/121

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