square root and cube root aptitude questions

1. The cube root of .000216 is:
A. .6 B. .06
C. 77 D. 87

Answer: Option B

Explanation:

 

 

(.000216)1/3 = 216 1/3
106

 

   = 6 x 6 x 6 1/3
102 x 102 x 102

 

   = 6
102

 

   = 6
100

= 0.06


2.  

What should come in place of both x in the equation x = 162 .
128 x
A. 12 B. 14
C. 144 D. 196

Answer: Option A

Explanation:

 

 

Let x = 162
128 x

Then x2 = 128 x 162

= 64 x 2 x 18 x 9

= 82 x 62 x 32

= 8 x 6 x 3

= 144.

x = 144 = 12.


3. The least perfect square, which is divisible by each of 21, 36 and 66 is:
A. 213444 B. 214344
C. 214434 D. 231444

Answer: Option A

Explanation:

 

L.C.M. of 21, 36, 66 = 2772.

Now, 2772 = 2 x 2 x 3 x 3 x 7 x 11

To make it a perfect square, it must be multiplied by 7 x 11.

So, required number = 22 x 32 x 72 x 112 = 213444


4. 1.5625 = ?
A. 1.05 B. 1.25
C. 1.45 D. 1.55

Answer: Option B

Explanation:

 

   1|1.5625( 1.25
    |1
    |-------
  22| 56
    | 44
    |-------
 245| 1225
    | 1225
    |-------
    |    X
    |-------

1.5625 = 1.25.


5.  

If 35 + 125 = 17.88, then what will be the value of 80 + 65 ?

A. 13.41 B. 20.46
C. 21.66 D. 22.35

Answer: Option D

Explanation:

 

35 + 125 = 17.88

35 + 25 x 5 = 17.88

35 + 55 = 17.88

85 = 17.88

5 = 2.235

80 + 65 = 16 x 5 + 65

= 45 + 65

= 105 = (10 x 2.235) = 22.35

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