SOLUTION: If two people can do a job in 12 minutes. And one person takes 30 minutes how long does it take the other person to do the job alone?

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Question 3906: If two people can do a job in 12 minutes. And one person takes 30 minutes how long does it take the other person to do the job alone?
Answer by ntnk(50) (Show Source):
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Together, they can to 1/12 of the job in a minute. One person does 1/30 in a minute. The unknown person does 1/x in a minute. To find out how much they do together, add:

Find a common denominator by multiplying each number by the LCD: 360x:

Simplify:

Subtract 12x from each side:

Simplify:

Divide each side by 18:

If the second person can do 1/20 of the job in one minute, he can do the entire job in 20 minutes.
Check: 1/20 + 1/30 = 1/12
Solved By: NtNk