00:01
Alright, in your question you're told that abraham can finish a painting job within five hours, jacob can finish a painting job within nine hours, and if they work together with isaac, they can finish painting in two hours total.
00:17
So isaac is the one we don't know.
00:20
We don't know how long it would take him to complete the job on his own.
00:26
In a work problem such as this, we can basically convert each of these to what part of a job each person can do in one hour.
00:35
So abraham can complete that in one fifth.
00:39
He completes one fifth of the job in an hour.
00:44
So it takes him five hours to do the whole job, so we're just taking one hour divided by five.
00:49
Jacob would be one ninth, and isaac would be one over x.
00:55
Now each of them are going to get to work for two hours, and they will complete the job.
01:01
So if i take each of these numbers times two, and then add them together, they will complete the total job, or one job completed.
01:19
That gives me the fraction two fifths plus two ninths plus two over x equals one...