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John can mow the lawn in 7 hours. His younger brother can do it in 4 hours. How long does it take the two of them when working together? hours
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John can mow the lawn in 7 hours. His younger brother can do it in 4 hours. How long does it take the two of them when working together?

hours

User Enriquev
by
7.6k points

1 Answer

10 votes
t/7 + t/4 = 1

Find common multiple of 7 and 4.
The common factor is 28

Multiply through

4t/28 + 7t/28 = 28/28

Get rid of the denominators.

4t + 7t = 28

11t = 28

t = 28/11
User Taknok
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