Question

If the length of the diagonal of a square is $20cm$, its perimeter is

• A. $40\sqrt{2}$ $cm$
• B. $20\sqrt{2}$ $cm$
• C. $80\sqrt{2}$ $cm$
• D. $10\sqrt{2}$ $cm$

Answer 1

The correct option is A $40\sqrt{2}$ $cm$

Perimeter $=4\times \text{side of square}$
$=4\times \frac{\text{diagonal}}{\sqrt{2}}cm=4\times \frac{20}{\sqrt{2}}\times \frac{\sqrt{2}}{\sqrt{2}}cm$
$=40\sqrt{2}cm$