SOLUTION: two cars traveled in opposite directions from the same starting point. The rate of one car was 10km less than the rate of the other. After 4 hours the cars were 600km apart. Find t

Algebra ->  Quadratic Equations and Parabolas  -> Quadratic Equations Lessons -> SOLUTION: two cars traveled in opposite directions from the same starting point. The rate of one car was 10km less than the rate of the other. After 4 hours the cars were 600km apart. Find t      Log On


   

Question 686131: two cars traveled in opposite directions from the same starting point. The rate of one car was 10km less than the rate of the other. After 4 hours the cars were 600km apart. Find the rate of each car
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
I think of one car as standing still and the other car
moving away from it at the sum of their speeds
Let +s+ = the speed of the faster car in km/hr
+s+-+10+ = the speed of the slower car in km/hr
---------------
+600+=+%28+s+%2B+s+-+10+%29%2A4+
+600+=+%28+2s+-+10+%29%2A4+
+600+=+8s+-+40+
+8s+=+640+
+s+=+80+
+s+-+10+=+70+
The speeds of the cars were 80 km/hr and 70 km/hr
check:
+d%5B1%5D+=+80%2A4+
+d%5B1%5D+=+320+
and
+d%5B2%5D+=+70%2A4+
+d%5B2%5D+=+280+
and
+d%5B1%5D+%2B+d%5B2%5D+=+320+%2B+280+
+d%5B1%5D+%2B+d%5B2%5D+=+600+
OK