00:01
For this question, you have been told, a cone -shaped paper drinking cup is to hold 100 cubic centimeter of water.
00:08
Find the height and the radius of the cup that will be made from the last, least amount of paper.
00:15
Least amount of paper.
00:17
Okay, let's start by finding the volume of the cone formula.
00:21
That is 1 over 3 into pi, r, square, h is equal to v.
00:32
Now we find h in terms of r.
00:34
So we make h the subject.
00:37
And we know that this is also equal to 100 because you're given the volume of 100 cubic centimeter.
00:41
So 100 is equal to 1 over 3 pi r square, h.
00:46
Making it's a subject, i get, h is equal to 300 over pi r square.
00:57
Now you have to use a surface area equation.
01:00
So let's say sa is equal to pi r square plus pi r l.
01:11
So now we have to find l using r in h by making l the subject.
01:18
So we'll say that l is equal to root of h square plus r square...