Problema Solution
betty can mop the floor in 7 minutes. together betty and nancy can op the floor in 5 minutes.how long does it take nancy to mop the floor alone?
Answer provided by our tutors
let
n = min that Nancy needs to mop the floor alone
the rate of Betty is 1/7 floors per min
the rate of Nancy is 1/n floors per min
the together rate is 1/5 floors per min
1/7 + 1/n = 1/5
by solving we find
n = 17.5 min
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Nancy can mop the floor in 17.5 min.