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

[TeenieWeenie]

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

V_avg = (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?

 

[Thaakisfox]

You forgot to multiply the 150 with 2, as the car goes 2 laps with that speed.

 

[TeenieWeenie]

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?

 

[Thaakisfox]

Yep that's right.

 

[TeenieWeenie]

Sweet! I had a feeling 337.5 was not right.
Thanks for the help Thaakisfox!

Problem solved!