Square and Cube Roots Quiz Set 019

Question 1

One-fourth of the square-root of which number is 0.9?

A

12.96.

B

12.56.

C

9.25.

D

9.50.

Soln.
Ans: a

Let the number be n. So \${1/4} × √n\$ = 0.9, which gives \$√n\$ = 4 × 0.9 = 3.6. so n = \$3.6^2\$ = 12.96.

Question 2

What is √(9720) × √(30)?

A

540.

B

450.

C

496.

D

196.

Soln.
Ans: a

We can see that √(9720) × √(30) is same as √(2 × 2 × 2 × 3 × 3 × 3 × 3 × 3 × 5 ) × √(2 × 3 × 5 ) which equals √(24 × 36 × 52), which equals (22 × 33 × 51), which gives 540.

Question 3

What is √0.0064?

A

0.08.

B

0.16.

C

0.016.

D

0.8.

Soln.
Ans: a

We can see that 0.08 × 0.08 = 0.0064, so square root is 0.08.

Question 4

How many 2 digit numbers are their whose squares end in 8?

A

0.

B

11.

C

10.

D

5.

Soln.
Ans: a

It is not possible for the square of any number to end in 2, 3, 7 or 8. Hence the answer is 0.

Question 5

If x = 0.3193, then what is the value of \$11x + √{16x^2 - 8x + 1}\$?

A

3.24.

B

0.324.

C

32.4.

D

3.16.

Soln.
Ans: a

By inspection, \$11x + √{16x^2 - 8x + 1}\$ is same as \$11x + √{({1 - 4x})^2}\$, which is same as 11x + (1 - 4x) = 1 + 7x = 3.24.