00:01
We're given information about a storage pool and a pipe that's filling it up.
00:05
So it's saying that one pipe is doing in 20 hours and a second and 15.
00:09
And now when we add a third, we're going to take only six hours for all three.
00:13
So we're going to kind of use the same as the work done formula, which is 1 over a plus 1 over b equals 1 over t, where a and b represent the time of the individual pipes and t is all together.
00:24
Now what makes this different is that we're now throwing in a third.
00:26
So instead of just saying 1 over a plus 1 over b equals 1 over t, we're going to throw in that third one of 1 over c.
00:34
So a and b will be the two pipes that are used, so the 20 and the 15.
00:39
So we'll have 1 over 20 plus 1 over 15.
00:44
Now this c is unknown.
00:46
It's the third pipe.
00:47
And then altogether it's going to be 1 over 6 for 6 hours.
00:51
So what we're going to do is get rid of these fractions by multiplying by the common denominator between 20.
00:56
20, 15, c, and 6, the common denominator would be 60.
01:01
So we're going to multiply through everything through by 60c...