SOLUTION: it takes doug 6 days to roof a house. if his son helps him,the job can be done in 4 days. how long would it take his son ,working alone,to roof a house?

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Question 65410: it takes doug 6 days to roof a house. if his son helps him,the job can be done in 4 days. how long would it take his son ,working alone,to roof a house?
Found 2 solutions by chitra, Edwin McCravy:
Answer by chitra(359) About Me  (Show Source):
You can put this solution on YOUR website!
The given data is:

Doug takes 6 days to complete the work.

So, in one day he completes 1/6 th of the work.

Let his son take x days to complete the job.

So, in one day he completes 1/x part of the work.


It is given that if both of them work together then they can complete the job in 4 days.

So, in one day they completes 1/4 th of the job.

1%2F6+%2B+1%2Fx+=+1%2F4

1%2Fx+=+1%2F4+-+1%2F6

1%2Fx+=+%283+-+2%29%2F12

1%2Fx+=+1%2F12

Therfore, x = 12

Hence, the son alone takes 12 days to complete the job.

Hence, the solution.

Happy calculating!!!!

Answer by Edwin McCravy(20054) About Me  (Show Source):
You can put this solution on YOUR website!
it takes Doug 6 days to roof a house. 

if his son helps him,the job can be done in 

4 days. how long would it take his son, 

working alone, to roof a house?



>>...it takes Doug 6 days to roof a house...<<



Therefore in ONE day, Doug roofs 1/6 of a house.



>>...if his son helps him,the job can be done 

in 4 days...<<



Therefore in 1 day, both working together, they 

can roof 1/4 of a house.



Since we know that in that ONE day when both of them

worked, Doug roofed 1/6 of a house that day. 



So in that ONE day his son roofed the rest of that

1/4 of a house, So we should subtract to find what

fraction of a house his son roofed that ONE day.



So the son roofed 1/4 - 1/6 of a house in that ONE day. 

Subtracting 1/4 - 1/6 = 3/12 - 2/12 = 1/12.



So the son roofed 1/12 of a house that ONE day, so 

working alone, it would take him 12 days, roofing 

1/12 of it every day.



Look, ma, no algebra, just subtraction of numerical

fractions! :-)



Edwin