Answer:
Peter and Ann will make 100 copies together in 3.33 hours.
Step-by-step explanation:
Let Ann took the time to make 100 copies of a certain document = x hours
Then per hour work done by Ann = ![\frac{1}{x}](https://tex.z-dn.net/?f=%5Cfrac%7B1%7D%7Bx%7D)
Time taken by Ralph to compete the work = 2 hours
So per work done by Ralph = ![\frac{1}{2}](https://tex.z-dn.net/?f=%5Cfrac%7B1%7D%7B2%7D)
Let the time taken by Peter to complete the work = y hours
Per hour work done by Peter = ![\frac{1}{y}](https://tex.z-dn.net/?f=%5Cfrac%7B1%7D%7By%7D)
It took 75 minutes or
hours by Ann, peter and Ralph together to complete the task.
Then per hour work done by all = ![\frac{60}{75}](https://tex.z-dn.net/?f=%5Cfrac%7B60%7D%7B75%7D)
And the equation representing per hour work done will be,
![\frac{1}{x}+\frac{1}{y}+\frac{1}{2}=\frac{60}{75}](https://tex.z-dn.net/?f=%5Cfrac%7B1%7D%7Bx%7D%2B%5Cfrac%7B1%7D%7By%7D%2B%5Cfrac%7B1%7D%7B2%7D%3D%5Cfrac%7B60%7D%7B75%7D)
![\frac{1}{x}+\frac{1}{y}+\frac{1}{2}=\frac{4}{5}](https://tex.z-dn.net/?f=%5Cfrac%7B1%7D%7Bx%7D%2B%5Cfrac%7B1%7D%7By%7D%2B%5Cfrac%7B1%7D%7B2%7D%3D%5Cfrac%7B4%7D%7B5%7D)
![\frac{1}{x}+\frac{1}{y}=\frac{4}{5}-\frac{1}{2}](https://tex.z-dn.net/?f=%5Cfrac%7B1%7D%7Bx%7D%2B%5Cfrac%7B1%7D%7By%7D%3D%5Cfrac%7B4%7D%7B5%7D-%5Cfrac%7B1%7D%7B2%7D)
![\frac{1}{x}+\frac{1}{y}=\frac{8-5}{10}](https://tex.z-dn.net/?f=%5Cfrac%7B1%7D%7Bx%7D%2B%5Cfrac%7B1%7D%7By%7D%3D%5Cfrac%7B8-5%7D%7B10%7D)
![\frac{1}{x}+\frac{1}{y}=\frac{3}{10}](https://tex.z-dn.net/?f=%5Cfrac%7B1%7D%7Bx%7D%2B%5Cfrac%7B1%7D%7By%7D%3D%5Cfrac%7B3%7D%7B10%7D)
Since per hour work done by Ann and Peter is
So time taken to complete the same work by both together will be
or 3.33 hours.