the diameter of a circle is 20 cm. What is the area of this circle in square centimeters?

diameter = 2*radius
radius=diameter/2
radius=20cm/2=10cm

area=pi*radius^2
area=3,14*10cm^2
area=314cm^2

the formula is pi * radius squared. Plug in the numbers, and turn the crank, and the answer will come out the end.

In other words - do your own homework.

A = π r²
A = π x 100
A = 314 cm²

area of circle = 22/7(10)²
= 22/7(100)
= 314.29

a = πr^2

π(20/2)^2
= 3.14(10)^2
= 3.14(100)
= 314 square centimeters

area = {pie}* (radius)^2
= 3.14* 10*10cm sq.
=314 cm sq

The diameter of the circle is 20 cm, so its radius is 10 cm. We know that the formula for an area of a circle is pi * r^2, so:
pi * 10^2 = 100 * pi = 314.159... square centimeters.

Hope I helped. :)
nadavs

100 x 3.1415926.................so on and so forth.

PI*R²=3.1416*10²~314.16cm²