Question

A circular garden has an area of $100\pi$ feet squared. What is the circumference of the garden in feet?

• A. $20$
• B. $10\pi$
• C. $20\pi$
• D. $400\pi$
• E. $2500\pi$

Answer 1

The correct option is C $20\pi$

Area of the circle $=$ $\pi r^2$
Hence, $100\pi$ feet squared $=$ $\pi r^2$
$\therefore r^2=100$
$r=\surd 100$
$r=10$ feet
and the diameter is $=$ $2r$ $=$ $2\times 10=20$ feet.
Circumference of a circle $=$ $\pi d$ $=$ $20\pi$
So the option C is the correct answer.