Question

Square root of $400$ is?

• A. $40$
• B. $25$
• C. $20$
• D. $100$

Answer 1

The correct option is C $20$

$400=2\times 200$

$=2\times 2\times 100$

$=2\times 2\times 2\times 50$

$=2\times 2\times 2\times 2\times 25$

$=2\times 2\times 2\times 2\times 5\times 5$

$=2^4\times 5^2$

$\Rightarrow$ $400=2^4\times 5^2$

$\Rightarrow$ $\sqrt{400}=\sqrt{2^4\times 5^2}$

$\Rightarrow$ $\sqrt{400}=2^2\times 5$

$\Rightarrow$ $\sqrt{400}=4\times 5$

$\Rightarrow$ $\sqrt{400}=20$