Question

David can proofread15 reports in an hour while Armando can proofread 37reports in an hour. If they have 400 reports to proofread,how much time will it take between the two of them?

Answer 1

Together, it would take them 6 hours

Answer 2

`7(9)/(13)\text{ hours}`

Explanation:

Given,

The number of reports proofread by David in one hour = 15,

While, the number of reports proofread by Armando in one hour = 37,

Total reports proofread by both of them in one hour = 15 + 37 = 52,

Also, the number of reports have to be proofread = 400

Hence, the time taken by both of them when they work together

`=\frac{\text{Total reports}}{\text{Number of reports by both of them in one hour}}`

`=(400)/(52)`

`=7(9)/(13)\text{ hours}`