Complex fractions and unit rates

Question

A truck driver drove 120 miles in 1 ¾ hours. what is the speed of the truck in miles per hour

Answer 1

120/(1 3/4) = 120/(7/4) = (4/7)(120) = 480/7 = 68 4/7 mph = about 68.6 mph

120 in 1 3/4 hours is a little faster than 120 in 2 hours or 120/2 = 60 mph. 68.6 is a little faster than 60 mph

Answer 2

Hi Emilee,

To find the speed in miles per hour, you need to divide the number of miles driven by the number of hours. As an example, 10 miles in 5 hours is equivalent to 2 miles per hour:

10 miles ÷ 5 = 2 miles

5 hours ÷ 5 1 hour

For your problem, that would be (recall that 1 3/4 is equal to 1.75):

120 miles ÷ 1.75 = 68.57 miles

1.75 hours ÷ 1.75 1 hour