Square and Cube Roots Quiz Set 010

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Question 1

One-fourth of the square-root of which number is 0.6?

 A

5.76.

 B

.5.24

 C

5.96.

 D

5.49.

Soln.
Ans: a

Let the number be n. So ${1/4} × √n$ = 0.6, which gives $√n$ = 4 × 0.6 = 2.4. so n = $2.4^2$ = 5.76.


Question 2

One-fifth of the cube-root of which number is 0.3?

 A

3.375.

 B

3.250.

 C

3.125.

 D

3.325.

Soln.
Ans: a

Let the number be n. So ${1/5} × √^3n$ = 0.3, which gives $√^3n$ = 5 × 0.3 = 1.5. so n = $1.5^3$ = 3.375.


Question 3

What is the value of $(√5 - 1/√5)^2$?

 A

$3{1/5}$.

 B

$3{2/5}$.

 C

$3{3/5}$.

 D

$3{4/5}$.

Soln.
Ans: a

I will give a general solution for any n. $(√n - 1/√n)^2$ is same as $({(√n)^2 - 1}/√n)^2$ which becomes $(n - 1)^2/n$. Putting n = 5, we get ${16/5}$, which is same as: $3{1/5}$.


Question 4

What is the value of $√{(11 - 2√3) × (11 + 2√3)}$?

 A

$√109$.

 B

9.

 C

10.

 D

√3.

Soln.
Ans: a

By inspection, we can easily see that the formula (a - b) × (a + b) can be used to simplify like this: $√{(11)^2 - (2√3)^2}$, which is same as $√{121 - (2^2 × 3)}$, which is same as $√{121 - 12}$ = $√109$.


Question 5

One-fourth of the cube-root of which number is 0.4?

 A

4.096.

 B

4.024.

 C

4.256.

 D

4.128.

Soln.
Ans: a

Let the number be n. So ${1/4} × √^3n$ = 0.4, which gives $√^3n$ = 4 × 0.4 = 1.6. so n = $1.6^3$ = 4.096.


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This Blog Post/Article "Square and Cube Roots Quiz Set 010" by Parveen (Hoven) is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.
Updated on 2017-05-17.

Posted by Parveen(Hoven),
Aptitude Trainer


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