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It would take one machine $4$ hours to complete a production order and another machine $2$ hours to complete the same order. If both machines work simultaneously at their respective constant rates, the time taken to complete the same order is ________ hours.

1. $2/3$
2. $3/4$
3. $4/3$
4. $7/3$

edited

## 1 Answer

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If we consider 100 units of work as total work. (To avoid fractions :3)

Then in 1 hour one machine does (100/4) = 25 units of work, while another one does (100/2)=50 units of work.

They together do 75 units of work in 1 hour ,so 100 units of work is done in (100/75) hours or 4/3 hours

So, (C)4/3 is the answer

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