SOLUTION: Two cars leave Naga City and travel opposite direction. Car A is average 12 kph less than Car B. After 3 hours, they are 396 km apart. What is the average rate of each car?

Algebra ->  Customizable Word Problem Solvers  -> Travel -> SOLUTION: Two cars leave Naga City and travel opposite direction. Car A is average 12 kph less than Car B. After 3 hours, they are 396 km apart. What is the average rate of each car?      Log On

Ad: Over 600 Algebra Word Problems at edhelper.com


    

Question 1062914: Two cars leave Naga City and travel opposite direction. Car A is average 12 kph less than Car B. After 3 hours, they are 396 km apart. What is the average rate of each car?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Think of this as one of the cars standing
still and the other traveling at the sum of their speeds.
Let +s+ = speed of car B in km/hr
+s+-+12+ = speed of car A in km/hr
------------------------------------------
+396+=+%28+s+%2B+s+-+12+%29%2A3+
+396+=+%28+2s+-+12+%29%2A3+
+396+=+6s+-+36+
+6s+=+432+
+s+=+72+
and
+s+-+12+=+60+
-------------------
Car B's average rate is 60 km/hr
Car A's rate is 72 km/hr
----------------------------
check:
+d%5B1%5D+=+60%2A3+
+d%5B1%5D+=+180+ km
and
+d%5B2%5D+=+72%2A3+
+d%5B2%5D+=+216+
and
+d%5B1%5D+%2B+d%5B2%5D+=+180+%2B+216+
+d%5B1%5D+%2B+d%5B2%5D+=+396+ km
OK