00:01
All right, so we've got the price of one gallon of gasoline was $4 .12 on january 1st, 2012.
00:11
And it rose at a rate of 6 cents per month, maybe not so bad compared to today, for every month, up until, for the next nine months, so up until september.
00:29
So we want to express the price as a function of time.
00:33
So p of t.
00:35
And then we'll let january be t equals zero.
00:40
And then t will be in months.
00:43
That'll make this the easiest.
00:45
And then we'll do the price in dollars.
00:48
These are just decisions you have to make.
00:50
You could do it in cents or you can do t in not months.
00:53
It would just be harder.
00:55
Okay, so 4 .12 is where it starts.
00:57
And then every month after january 1st, we're adding $0 .06.
01:07
So there's the price as a function of time.
01:10
And then that's the price of one gallon.
01:14
So what was the price of 15 gallons on april 1st? so that's p of 4 is the price of one gallon, and we want 15 times that to get the price of 15 gallons.
01:24
So we do 15 times 4 .12 plus 0 .0 .0.
01:29
Six times four.
01:32
So that's 15 times 4 .36.
01:39
And i don't want to do that in my head, so i'll just type that into my calculator to get $65 .40.
01:51
Terrible to fill up a tank and get for that much...