Posted by Jay on Monday, July 13, 2009 at 3:41pm.
Stephanie can clean a pool in 1 hour , and Mark can clean the same pool in 1.5 hours. If the rate at which they work together is the sum of their rates working separately, how many minutes should they need to clean the pool if they work together? (1 hr=60 min)

Math  Marth, Monday, July 13, 2009 at 3:51pm
Stephanie cleans at the rate of 1 pools/hr.
Mark cleans at the rate of 1/1.5, or 2/3 pools/hr.
Their combined rate is 5/3 pools/hr
If r is the rate, t is time, and p is the number of pools, then
r = p/t
(5/3pools/hr) = (1 pool)/t
t = 3/5hr
t = 60*3/5 = 36min
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