Practice!

Sample Problem

Lizzie wants to bike to her friend’s house but doesn’t know which route is faster. She could travel 5.5 miles at a speed of 12mph if she takes the main roads or 4.3 miles at 10mph if she takes short but bumpy roads. Which route should Lizzie take in order to reach her friend’s house in the least amount of time? Use the formula d = rt.

Solution

Use the formula d = rt.

Main roads:  5.5 = 12t

t = 5.5/12≈0.46 h

Bumpy roads: 4.3 = 10t

t = 0.43 h

0.43 < 0.46, so Lizzie  should take short bumpy roads.