Question 446383
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If Jill fills a pool with water in 30 min, Jack fills a pool with water in 45 min and John fills a pool 
with water in 1 hour and 30 min. How long will it take if they work together ?
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        I will solve it in more understandable way than @mananth does it in his post.



Jill makes full job in  30 minutes - hence,  Jill makes  1/30  of the job per minute.


Jake makes full job in  45 minutes - hence,  Jake makes  1/45  of the job per minute.


John makes full job in  90 minutes - hence,  John makes  1/90  of the job per minute.


Working together,  they make


          {{{1/30}}} + {{{1/45}}} + {{{1/90}}} = {{{3/90}}} + {{{2/90}}} + {{{1/90}}} = {{{6/90}}} = {{{1/15}}}


of the job per minute.


Hence,  it will take  15 minutes for the three participants to complete the job working together.



               Solved - hip-hip-hooray  ( ! )