Grade 7 - Mathematics 9.7 Diameter of a Circle - I

Example:
The perimeter of a semicircle is 30 cm. Find its diameter.

Solution:
Let the radius of the circle be r cm.
Given that,
The perimeter of the semicircle (2+p)r = 30cm.
Þ (2 + 22/7) * r = 30
Þ 36/7 * r = 30.
\ (30*7)/36
Þ 5.8333.......cm.
Þ 5.8 cm. (approximately)
\ Diameter of the semicircle = 2r
= 2 * 5.8
= 11.6 cm.

Directions: Read the above example carefully and answer the following questions. Draw 6 different semicircles. Find the radius and perimeter of each of them.