Problem Driver Must Average 337.5 km/h for Last 4 Laps

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To qualify for a race, a driver must average 200 km/h over six laps. After averaging 150 km/h for the first two laps, the driver needs to calculate the required average speed for the last four laps. The correct calculation shows that the driver must average 225 km/h over those laps, not 337.5 km/h as initially thought. The discussion highlights the importance of accurate calculations in determining lap speeds. The problem was successfully resolved with the help of a forum member.
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Problem solved; thanks Thaakisfox!

Homework Statement


A race car driver must average 200km/hr for six laps of the race track to qualify for a race. If he averages only 150 km/h for the first two laps, calculate the average velocity he must have over the last four laps in order to qualify.

Homework Equations


Vavg = (X2 - X1) / (T2 - T1)

The Attempt at a Solution


Set V average = 200 km/hr.
200 = [150+ 4(v)]/6
1200 = 150+4v
1350/4 = V for last 4 laps?

337.5 km/h per lap for the last 4 laps?
 
Last edited:
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You forgot to multiply the 150 with 2, as the car goes 2 laps with that speed.
 
Alrighty. I double checked and ended up with this.

200 km/h = [300km/h + 4(v)] / 6
1200 = 300 +4v
900 = 4v
225 km/h = v per lap needed to average at 200km/h for 6 laps.

Does that sound right?
 
Yep that's right.
 
Sweet! I had a feeling 337.5 was not right.
Thanks for the help Thaakisfox!

Problem solved!
 

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