00:01
All right, so what they tell us is the rate of rainfalling.
00:03
So whenever it's a rate, it's a derivative.
00:05
So they give us the rate is 8 times root 2t minus 32 t cubed.
00:14
And we want to find an expression for the actual amount of rainfall, which is going to be given by r of t.
00:21
And they give us a hint that r of zero is zero.
00:25
So let's start taking an integral.
00:28
T to the one half is what's here.
00:31
So we get t to the three halves.
00:33
We have an eight root two.
00:36
Multiply by two thirds.
00:39
Minus 32, let's see, 32 over 4, right? it's going to be t to the 4.
00:44
So 8 t to the 4.
00:46
The derivative of that is 32 t cubed.
00:48
That's good...