Hi im having problem with this question and keep getting the wrong answer.(adsbygoogle = window.adsbygoogle || []).push({});

1. A racecar driver must average 200km/h for four laps to qualify for a race. Because of engine trouble, the car averages only 170km/h over the first two laps. What average speed must be maintained for the last two laps?

Ok what i had done is this:

200=(170 +x)/2

x=230km/h

Well my teacher said this is wrong and that we need to think of this question in terms of Vavg=(d1 +d2)/(t1+t2) to figure it out but i dont understand how to do that since we dont have time or distance. Apparently we are to try and think of an equation that will have constant terms cancelling eachother out to get the right answer but i cant figure it out. If anyone could show me how to do this question i would appreciate it greatly!

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# Homework Help: Average Speed Problem

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