Question 151235
If tom can fill a swimming pool in 30 min, sally can fill one in 45 min, and Joe can fill one in 90 min. How long will it take for them to fill a swimming pol together?
;
Let t = time required if they work together
Let the full pool = 1
:
{{{t/30}}} + {{{t/45}}} + {{{t/90}}} = 1
Multiplying the equation by 90 will get rid of the denominators, results:
:
3t + 2t + t = 90
:
6t = 90
t = {{{90/6}}}
t = 15 min
;
:
Check solution:
{{{15/30}}} + {{{15/45}}} + {{{15/90}}} =
{{{45/90}}} + {{{30/90}}} + {{{15/90}}} = 1