Problema Solution
It takes a man 5 hours to wash and wax the family car. If his teenage son helps him, it only takes 2 hours. How long would it take the son, working alone, to wash and wax the car?
Answer provided by our tutors
let
s = the hours that the son needs to wash and wax the car alone thus his rate is 1/s cars per hour
the rate of the father is 1/5 cars per hour
the together rate is 1/2 cars per hour
1/s + 1/5 = 1/2
by solving we find
s = 10/3 hr
s = 3 hr 1*60/3 min
s = 3 hr 20 min
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the son will need 3 hr and 20 min to wash and wax the car alone.