SOLUTION: If one riveter can do a job in 12 days, and a second riveter can do it in 16 days, how long would it take them to do it together?

Question 135287This question is from textbook Basic Technical Mathematics with Calculus
: If one riveter can do a job in 12 days, and a second riveter can do it in 16 days, how long would it take them to do it together? This question is from textbook Basic Technical Mathematics with Calculus

Found 2 solutions by solver91311, ptaylor:
Answer by solver91311(24713) (Show Source): You can put this solution on YOUR website!
If the first guy can do the job in 12 days, then he can do of the job in 1 day. Likewise, the other guy can do of the job in 1 day.

Together, they can do of the job in 1 day. Which means that they will take days to do the whole job. Just add the two fractions and turn the result over (switch numerator and denominator) to do the arithmetic.

Hint: 12 = 2 X 2 X 3 and 16 = 2 X 2 X 2 X 2, so 2 X 2 X 2 X 2 X 3 is your lowest common denominator.

Answer by ptaylor(2198) (Show Source): You can put this solution on YOUR website!
Let x=amount of time needed for both working together
One riviter works at the rate of 1/12 job per day
The second riviter works at the rate of 1/16 job per day
Together they work at the rate of 1/12 + 1/16 job per day, or
4/48 + 3/48 = 7/48 of the job per day. So our equation to solve is:
(7/48)x=1 (1 job, that is) multiply each side by 48
7x=48 divide both sides by 7
x=6 6/7 days or 6.8571 days
Hope this helps -----ptaylor
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