D = 10 cm, find out the circumference and area of the circle

D = 10 cm, find out the circumference and area of the circle

C = π D S = the square of π R
=3.14 × 10 = 3.14 × 5 square
=31.4 (CM) = 78.5 (cm2)

The circumference of a semicircle is 20.56 decimeters. What is the diameter of the semicircle?

Let the radius of a circle be x decimeters
Then 2x + π x = 20.56
Then x = 20.56 △ 5.14
x=4
So the diameter of the semicircle is 2x = 8 decimeters

The circumference of a semicircle is 20.56 cm. What is the diameter of the semicircle?

20.56÷（3.14+2）×2
=4×2
=8 cm
The diameter is 8 cm