what is the perimeter of a circle of radius 10.5 cm?

Hi,

The perimeter of a circle is called the circumference. Its formula is C = 2πr, so if r = 10.5 cm, then C = 2π(10.5) = 21π. If you replace π with its decimal value then 21π = 65.973 cm.

So the answer is 21π or 65.973 cm.

I hope that helps!! :-)

P = 2 π r
P = 21 π cm
P = 21 (22/7) cm
P = 66 cm

You are finding the circumference (perimeter) of the circle
The formula for the circumference of the circle is 2πr.
So if you take the formula,
2πr and substitute in the numbers.
π is 3.142
r is your radius, 10.5cm
2πr=circumference
2 x 3.142 x 10.5= circumference
circumference= 65.982cm#

Perimeter of circle, c = 2 pi r where pi is constant and it's value is 3.14 or 22/7 and r is radius of circle.
c = 2 10.5 × 22/7
= 66 cm

Circumference = radius x 2 x π

10.5 x 2 x π
= 21 x 22/7
= 462/7
= 66 cm

the preimeeter of circle is considered to be the circumference of the circle;
C = 2(pi)(r) = 2(3.1416)(10.5) = 65.973cm