Question 278501
A swimming pool can be filled in 12 hours if water enters through a pipe alone,
 or in 28 hours if water enters through a hose alone.
 If the water is entering through both the pipe and the hose,
 how long will it take to fill this pool?
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Let t = time required when both are used
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Let the completed job (a full pool) = 1
:
A typical mixture equation
{{{t/12}}} + {{{t/28}}} = 1
Multiply equation by 84 to clear the denominators, results
7t + 3t = 84
t = {{{84/10}}}
t = 8.4 hrs working together
;
:
Check solution
{{{8.4/12}}} + {{{8.4/28}}} = 
.7 + .3 = 1