Need to find formula to find rate for Susan.

Question

Susan left the airport and drove east.
Cody left three hours later driving 36 mph
faster in an effort to catch up to her. After
two hours Cody finally caught up. What
was Susan's average speed?

Answer 1

Hey Ricardo! In order to solve this question, we need to understand a few things about this problem!

First, by using Cody's speed and travel time, we can figure out how far Cody and Susan traveled because if Cody caught up to Susan, they both would have traveled the SAME distance. 

 

So 36mph * 2h = total distance traveled

 

Next, we know that Cody is driving faster than Susan, which means that we should expect an average speed for Susan that is slower than Cody's, right? 

 

Finally, if Cody starts traveling 3 hours AFTER Susan starts traveling and catches up to her AFTER 2 hours, it means that Susan has traveled for 5 hours in total! 

 

To figure out Susan's average speed, we just need to divide the total distance traveled by 5 hours: (36*2)/5 = Susan's average speed. 

 

I hope this helps!