<PRE><B>Question 1140553</B>
let t be the hours it takes both pumps working together to drain the pool
:
1/6 + (1/14) = (14 + 6)/84 = 20/84 = 10/42
:
working together, the pumps do 10/42 of the job in 1 hour
:
also working together they do 1/t per hour, then
:
10/42 = 1/t
:
invert the two fractions and solve for t
:
t = 42/10
:
t = 4.2
:
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working together, they empty the pool in 4.2 hours
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:
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