0:00
If necessary.
00:01
So for these shapes, i'm going to use the surface area formula for a cone.
00:08
So here is the formula right here.
00:10
Surface area equals pi times r times s and then plus pi times r squared.
00:19
So i have to figure out what the slant height is.
00:23
So i have to use the pythagorean theorem first.
00:25
So 10 squared plus 25 squared equals c squared, which is.
00:30
This is c the slant height or s we should call it s squared for the slant height.
00:36
So 100 plus 25 times 25 is 625 equals s squared plus 100.
00:48
So 725 equals s squared.
00:52
So then the square root of 725 is 20.
00:59
I'll round it to the nearest one's place.
01:01
So, or actually, if i round it to the 10th place, 26 .9.
01:07
So 26 .9.
01:10
So now i'm going to do surface area equals 3 .14 times the radius, which is 10, times the slant height, which is 26 .9, plus, so i have all of that plus 3 .14 times 10 squared.
01:29
So surface area equals 3 .14 times 10 times 26 .9, and that is 844 .66 plus 3 .14 times 10 squared, which is 100...