Problema Solution
A person X can clean up all of the crime in a city in 4 hr working alone. Person Y can do the same job alone in 10 hr. If person Y starts crime fighting at 9 A.M. and person X joins him at 12 Noon, at what time will they have all the crime cleaned up?
Answer provided by our tutors
the rate of person X is 1/4 of crime per hour
the rate of person Y is 1/10 of crime per hour
Y starts at 9 AM and until 12 Noon that is 3 hours works alone
let t = the time that X and Y work together (in hours)
(t + 3)*(1/4) + t*(1/10) = 1
by solving we find:
t = 5/7 hr
t = 5*60/7 min
t = 43 min approximately
click here to see the step by step solution of the system of equations:
the crime will be all cleared up at 12:43 pm.