Speed question

Question

Two friends decided to go on a road trip. They travelled along a highway for 2 hours and then along the side roads for another 4 hours. The total length of their trip was 250km. If they travelled 50km/h faster on the highway than on the side roads, what speeds were they travelling at for each road? 

Answer 1

Maadinee,

 

The main equation you have to remember is that d= r*t.  The distance that  was traveled on the highway plus the distance traveled on the side roads  is 250 .  So we need to find a way to 

express the distance.  We know the time for both parts of the journey.  We do not know the rates.

Right now, our equation looks like this:

250 = 2* hwy rate + 4 * side road rate.

We know that the hwy rate is 50 more than the side road rate, so let s = side road rate and s +50 = the hwy rate.

250 = 2 (s+50) + 4 s

Solve this for s.  Then add 50 more and get the highway rate.

 

Check your answer by plugging into the main equation and making sure you get 250.

 

You can do it!  Let me know if you have any more problem with it.

 

Mary