Question

What is the formula to find the perimeter of a semicircle with radius $r$?

• A. $\pi r$
• B. $2\pi r$
• C. $r(\pi +2)$
• D. $2(\pi +r)$

Answer 1

Answer: (C)

$r(\pi +2)$

Circumference of a circle $=2\pi r$

Circumference of semi circle $=\frac{2\pi r}{2}=\pi r$

$\therefore$ The length of curved line is $\pi r$

The length of straight line(diameter)$=2r$

The total perimeter of a semi circle is $\pi r+2r=r(\pi +2)$