Question 207027
Jim can fill a pool carrying buckets of water in 30 minutes.
 Sue can do the same job in 45 minutes.
 Tony can do the same job in 1 1/2 hours.
 How quickly can all three fill the pool together?
;
Let t = time (in minutes) required working together
:
let the completed job (full pool) = 1
{{{t/30}}} + {{{t/45}}} + {{{t/90}}} = 1
Multiply equation by 90, results
3t + 2t + t = 90
:
6t = 90
t = {{{90/6}}}
t = 15 min