If you would like to know how much does the object travel in one hour, you can calculate this using the following steps:
4/5 miles ... half an hour = 30 minutes
x miles = ? ... one hour = 60 minutes
4/5 * 60 = 30 * x /30
x = 4/5 * 60 / 30
x = 4/5 * 2
x = 8/5 = 1 3/5 miles
The correct result would be 1 3/5 miles in one hour.