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Worker $A$ takes $8$ hours to do a job. Worker $B$ takes $10$ hours to do the same job. How long it take both $\text{A&B}$, working together but independently, to do the same job?

1. $40/9$ days
2. $40/7$ days
3. $7.5$ days
4. $8.5$ days

It should be 40/9 hrs not days
164 points

A =$\frac{1}{8}$        $B=\frac{1}{10}$

We have to find  A+B = $\frac{1}{8} +\frac{1}{10} = \frac{9}{40}$

Time taken for both A and B to do the same work is $\frac{40}{9}$ hours
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