SOLUTION: A car leaves a country town travelling at 60km/h. Two hours later a second car leaves the town and catches up to the first car in five hours. Find the speed of the second car.

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Question 599478: A car leaves a country town travelling at 60km/h. Two hours later a second car leaves the town and catches up to the first car in five hours. Find the speed of the second car.
Found 2 solutions by josmiceli, Nihal@SriLanka:
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Let +s+ = the speed of the 2nd car in km/hr
Let +d+ = distance in km 2nd car travels until it catches 1st car
The 1st car's head start is +60%2A2+=+120+ km
Start a stopwatch when the 2nd car leaves town
1st car:
+d-+120+=+60%2A5+
+d+=+300+%2B+120+
+d+=+420+km
2nd car:
+d+=+s%2A5+
+420+=+5s+
+s+=+84+
the speed of the 2nd car is 84 km/hr

Answer by Nihal@SriLanka(22) About Me  (Show Source):
You can put this solution on YOUR website!
The problem could also be solved without resorting to algebraic notation.

By the time the second car catches up with the first car it has traveled a total of seven hours at a speed of 60 km per hour which implies it had traveled a total distance of 60 into 7, i.e. 420 kilometers. Since the second car has to catch up this distance in 5 hours it has to travel at a speed of 420 by 5, i.e. 84 km per hour.