9514 1404 393
Answer:
1 3/7 hours
Explanation:
Sarah finishes 1/2 the report in 1 hour; Chad finishes 1/5 of the report in 1 hour. So, in each hour, they finish ...
1/2 + 1/5 = 7/10
of the report.
It will take 1/(7/10) = 10/7 = 1 3/7 hours for them to finish the report together.
_____
As always, the applicable relation is ...
time = quantity/rate
time = 1 report/(7/10 report/hour) = 10/7 hours