math word problem

Question

Ming left the movie theater and traveled
toward the ocean. Mofor left two hours
later traveling 25 mph faster in an effort to
catch up to her. After four hours Mofor
finally caught up. What was Ming's
average speed?

 

 

Answer 1

Distance = rate x  time

 

If we let Ming's speed = x, then Mofor's speed is x + 25

If we let Ming's time = t, then Mofor's time will be (t - 2) because Mofor left 2 hours later

 

They both will have traveled the same distance when t = 4 because Mofor catches up with Ming after 4 hours. 

 

Now let's use our formula for distance:

 

xt = (x + 25)(t - 2)   when t = 4

4x = (x + 25)(4 - 2)

4x = 2(x + 25)

4x = 2x + 50

2x = 50

x = 25   So Ming's avg. speed was 25 mph