Question 198028
A pool can be filled by one pipe in 3 hours and by a second pipe in 6 hours.
 How long will it take using both pipes to fill the pool.
:
Let t = time required when both pipes are used
:
Let the completed job (full pool) = 1
:
Each pipe fills a fraction of the pool, the two fractions add up to 1
{{{t/3}}} + {{{t/6}}} = 1
Multiply equation by 6 to get rid of the denominators,
6*{{{t/3}}} + 6*{{{t/6}}} = 6(1)
cancel the denominators and you have:
2t + t = 6
:
3t = 6
t = {{{6/3}}}
t = 2 hrs working together
;
:
Check solution:
2/3 + 2/6 = 1