Help solve the world problem?

Question

A homeowner estimates that it will take her 9 days to roof her house. A professional roofer estimates that he could roof the house in 4 days. How long will it take if the homeowner helps the roofer?

Answer 1

The world has too many problems for you to solve. :-)



Each day the roofer can do 1/4 of the roof, the homeowner 1/9. Add them together, and they can do 9/36+4/36 of the roof each day. They can complete the job in 36/13 days, 2 10/13.

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Answer 2

Homeowner can roof her house in 9 days while a professional roofer can do it in 4 days.

That means that they can do.



Homeowner = 1/9 of the job per day

Roofer = 1/4 of the job per day



Add these up,



1/9 + 1/4 = 1/x

13/36 = 1/x

13x = 36

x = 2.77 days.



They will take 2.77 days to roof the house.

Answer 3

x = the number of days to finish the one job



The owner works at a speed of 9 days per job



The roofer works at a speed of 4 days per job



(x / 9) + (x / 4) = 1



(1 / 9) x + (1 / 4) x = 1



(4 / 36) x + (9 / 36) x = 1



(13 / 36) x = 1



x = 36 / 13



x = 2.77 days <==================

Answer 4

Homeowner takes 9 hours to complete a roof that is

within 1 hour he can finish only 1/9 th of the roof.

roffer takes 4 hours to complete the roof that is

within 1 hour he can finish only 1/4 of the roof, so

if both works together,

they can finish (1/9+1/4) 13/36th of the roof so

in 1 hour (they finished) 13/36 of roof

in x hour ( they finishes) 1 (the whole) roof

Using ratio of propotion, we get:

x*(13/36) = 1*1 = 1 or x = 36/13 = 2.8 hours <= answer

Answer 5

2 and 3/4 days

Answer 6

The important thing in these questions is to realize that what they are doing to answer it is, they determine what PART of the job each person can do in a given amount of time...'A' takes 3 hours, so 'A' can do 1/3 of the job in one hour...etc.