It takes Doug 6 days to reroof a house. If Doug's son helps him, the job can be completed in 4 days. How long would it take Doug's son, working alone, to do the job?



Answer :

rate of doug is 1 roof in 6 days.
which means he could do 2/3 of a roof in 4 days, whixh means his son does 1/3 of a roof in 4 days, whhich is 1 roof per 12 days.
[tex]4( \frac{1}{6}+ \frac{1}{x})=1[/tex]
[tex] \frac{1}{6} + \frac{1}{x} = \frac{1}{4} [/tex]
[tex] \frac{1}{x} = \frac{1}{12} [/tex]
x=12

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