00:01
I want to find the area of a circle.
00:04
That formula is pi r squared.
00:08
So you can see i need to find r, which is the radius, to use my formula.
00:14
In number 12, 13 rather, i'm sorry, i'm told circumference is 31 .4 feet.
00:25
So i'm told to use 3 .14 for pi.
00:29
So i know the formula for circumference is 2 pi r.
00:35
So 31 .4 is going to equal 2 times 3 .14 times r.
00:46
2 times 3 .14 is 6 .28.
00:53
Divide both sides.
00:55
31 .4 divided by 6 .28 gives me a radius of 5.
01:01
So my area is pi times 5 squared or pi times 25.
01:11
And if i want to use 3 .14 for pi again, i'm just going to multiply 25 times 3 .14.
01:21
And i have an area of 78 .5 square feet...