smc

Question

Mr. Lopez has a choice of two routes to get to work. Route A is 6 miles long, and his average speed along this route is 30 miles per hour. Route B is 5 miles long, and his average speed along this route is 40 miles per hour, except for a 12-mile stretch in a school zone where his average speed is 20 miles per hour. By how many minutes is Route B quicker than Route A?

Accepted Answer

If Mr. Lopez chooses Route A, then he will spend 630=15 hour, or 1560=12 minutes. If Mr. Lopez chooses Route B, then he will spend 9/240+1/220=1180 hour, or 118060=814 minutes. Therefore, Route B is quicker than Route A by 12-814=3 34 minutes.