SOLUTION: A homeowner estimates that it will take 9 days to roof his house. A professional roofer estimates that he could roof the house in 5 days. How long will it take if the homeowner hel

Algebra ->  Percentage-and-ratio-word-problems -> SOLUTION: A homeowner estimates that it will take 9 days to roof his house. A professional roofer estimates that he could roof the house in 5 days. How long will it take if the homeowner hel      Log On


   

Question 1095245: A homeowner estimates that it will take 9 days to roof his house. A professional roofer estimates that he could roof the house in 5 days. How long will it take if the homeowner helps the roofer?
Found 2 solutions by richwmiller, josgarithmetic:
Answer by richwmiller(17219) About Me  (Show Source):
You can put this solution on YOUR website!
Considering that the non professional homeowner will slow down the pro and ruin material to boot. I would guess at least double the time. So I'll say 10 days plus weekends. So two full weeks at least.

Answer by josgarithmetic(39618) About Me  (Show Source):
You can put this solution on YOUR website!
Only if the combined rates are truly additive,...

1%2Fx=1%2F9%2B1%2F5, rate unit being JOBs per DAY
-
9%2A5%2Ax%281%2Fx%29=9%2A5%2Ax%281%2F9%2B1%2F5%29
45=5x%2B9x
14x=45
x=45%2F14

x=3%263%2F14; just a little more than 3 days.