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How much time did it take a certain car to travel 400 [#permalink]
19 Jun 2006, 09:07
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How much time did it take a certain car to travel 400 kilometers?
1. Car traveled the first 200 kilometers in 2.5 hours
2. If car's average speed was 20 kilometers greater, it would have taken 1 hour less.
Please explain your answer. I got it right, but what is the best equation to use here?
B is my answer as well
1) is not enough for us since we do not know the speed with which the car drove the second part of the route (we are not said that the speed was constant, although if it would have been said then it would be sufficient as well)
2) is enough:
we can construct an equation (v is fpr speed)
a quadratic equation. if we solve it we will get that the speed is v=80