To qualify for the indianapolis 500 race, a car must average 350 km/hr for four laps. if a driver averages 320 km/hr for the first two laps, what average speed must be achieved for the final two laps in order to qualify?

In this case, the car velocity is 320km/hr (speed1) at the two laps (time1) and you want to make its average velocity (speed2) for the last 2 laps (time2) to fulfill the condition of 350km/h average speed. Then the formula to solve this question would be:

average 4 laps speed * laps = speed1 * laps1 + speed2 * laps2

350km/h * 4 = (320km/h*2) + (speed2 * 2)

2*speed 2 = 1400km/h - 640km/h = 760km/h

speed2 = 380km/h