Square and Cube Roots Quiz Set 013

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Question 1

If $√5$ = 2.24, then what is the value of ${√5}/2$ − $4/{√5}$?

 A

-0.671.

 B

+0.671.

 C

6.71.

 D

-6.71.

Soln.
Ans: a

The given expression can be simplified to ${{(√5)^2} - 2 × 4}/{2 × √5}$, which is same as ${5 - 8}/{2 × √5}$, which is same as ${-3/{2 × √5}$. Rationalizing, we get ${-3/{2 × √5} × {√5/√5}$ which gives ${-3√5}/10$ which = -0.671.


Question 2

What is the value of ${√16/6}$ × ${5/√4}$ × ${6/√25}$?

 A

2.

 B

3.

 C

1.

 D

4.

Soln.
Ans: a

The given expression can be simplified to ${√2^4/6}$ × ${5/√2^2}$ × ${6/√5^2}$, which is same as ${2^2/6}$ × ${5/2}$ × ${6/5}$, which cancels to 2.


Question 3

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 4

What is the value of ${√5}/3$ − $2/{√5}$?

 A

${-1√5}/15$.

 B

${+1√5}/15$.

 C

${-2√5}/15$.

 D

${+2√5}/15$.

Soln.
Ans: a

The given expression can be simplified to ${{(√5)^2} - 3 × 2}/{3 × √5}$, which is same as ${5 - 6}/{3 × √5}$, which is same as ${-1/{3 × √5}$. Rationalizing, we get ${-1/{3 × √5} × {√5/√5}$ which gives ${-1√5}/15$


Question 5

If x = 0.7342, then what is the value of $11x + √{16x^2 - 8x + 1}$?

 A

6.14.

 B

12.28.

 C

3.14.

 D

3.07.

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 = 6.14.


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This Blog Post/Article "Square and Cube Roots Quiz Set 013" by Parveen (Hoven) is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.
Updated on 2019-08-18.

Posted by Parveen(Hoven),
Aptitude Trainer


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