Question

A machine uses gasoline at a rate of 1/5 gallon an hour. So far 9/10 of a gallon has been used. How many hours has the machine operated?

1. The machine was operated for  4.5 hours
A machine uses gasoline at a rate of 1/5 gallon per hour
The number of hours it will take the machine to use 9/10 gallon can be calculated as follows
1/5 = 1
9/10= x
cross multiply
1/5x= 9/10
0.2x= 0.9
x= 0.9/0.2
x= 4.5
Hence the machine was operated for 4.5 hours