SOLUTION: A drain can empty a swimming pool in 8 days. A second drain can empty this pool in 4 days. In how much time will the two drains working together empty the pool?

Question 512051: A drain can empty a swimming pool in 8 days. A second drain can empty this pool in 4 days. In how much time will the two drains working together empty the pool?
Answer by oberobic(2304) (Show Source): You can put this solution on YOUR website!
These type of problems are fraction problems.
One drain can do the whole job in 8 days, so it does 1/8 per day.
Another drain can do the job in 4 days, so it does 1/4 per day.
x = number of days
.
(1/4 + 1/8) * x = 1 whole job
.
12/32 * x = 1
.
x = 32/12 = 8/3
.
Working together they can drain the pool in 8/3 = 2 2/3 days.
.
Check this answer.
(1/4 + 1/8) * 8/3 = 1 ??
(12/32)*8/3 = 96/96 = 1
correct!
.
Done.
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