Question 6471: Hi there,
I am confronted with the following question:
"A job takes 4 hrs for two people working together. If one person works alone he can do the job in 6 hrs. How long will it take the other person working alone to complete the job?"
I don't really know how to approach this question. It seems so simple yet I can't seem to figure out why the answer is 12 hrs. Please help me out.
Thanks in advance,
Mike
Answer by Earlsdon(6294)   (Show Source):
You can put this solution on YOUR website! This kind of problem can be solved by asking "how much of the job is done in 1 hour?"
Let's call the two people Sam and Eric, or S and E for short.
So, S and E together can do the whole job in 4 hours. This means that they can do 1/4 of the job in 1 hour.
Now, Sam can do the whole job in 6 hours. This means that Sam can do 1/6 of the job in 1 hour.
To find find out how much of the job Eric can do in 1 hour, simply subtract what Sam can in 1 hour from what Sam & Eric can do together in 1 hour.
(S + E) - S = E
1/4 - 1/6 = 3/12 - 2/12 = 1/12
So, Eric can do 1/12 of the job in 1 hour, which means it will take him 12 hours to do the whole job.
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