Use the following formula to calculate the average speed of the automobile:
average speed = ditance/time
in this case, you have:
distance = 471 miles
time = 8 1/2 hours = 8.5 hours
replace teh previous values into the formula for the average speed:
average speed = (471 mi)/(8.5 h) = 55.41 mph
average speed ≈ 55 mph
Hence, the average speed of the automobile is 55 mph.