Ronald rode away from home in a car at the rate of 32 miles per hour. He walked back at the rate of 4 miles per hour. The round trip required 2.25 hours. How far did Ronald ride?

Question

I want to know how to do this by using the chart method, (D=R•T)

Answer 1

 

The diagram represents the question. AC represents the time for the round trip=2.25 hrs.

AB represents the outward trip and BC the return walk.

The slope of AB is R=32 mph and the slope of BC is R=4 mph.

The shorter segment of AC has a length (time) of D/32 where D is the distance of the trip, and the longer segment has a length of D/4.

So D/32+D/4=2.25=9/4. Multiply by 32: D+8D=72, so 9D=72 and D=8 miles.