to qualify for a race, a car must average 350 km/hr for four laps. If a driver averages 285 km/hr for the first two laps, what average speed must be achieved for the final two laps in order to qualify?
avg speed=distance/time
350=4laps/(time2+time4)
time for first two time2=distance/285=2laps/285
time for last two laps=2laps/V
350=4/(2/285+2/V)
2/285+2/V=4/350
2/v=4/350-2/285
1/V=2/350-1/285
V=350*285/(2*285-350) and you can finish it.
453.41
To find the average speed for the final two laps, you need to determine the total distance covered by the car in four laps and then divide it by the total time taken.
First, let's calculate the distance covered by the car in the first two laps. Since the driver averages 285 km/hr, we can calculate the distance covered using the formula:
Distance = Speed × Time
Distance = 285 km/hr × 2 hr = 570 km
Since the car needs to average 350 km/hr for four laps, the total distance covered by the car in four laps would be:
Total distance = 350 km/hr × 4 hr = 1400 km
Now, let's find out how much distance the car needs to cover in the final two laps to meet the qualification requirement. Since the car has already covered 570 km in the first two laps, subtracting this from the total distance gives us:
Remaining distance = Total distance - Distance covered in first two laps
Remaining distance = 1400 km - 570 km
Remaining distance = 830 km
Since there are two laps remaining, the average speed for these two laps should be:
Average speed = Remaining distance / Time
Average speed = 830 km / 2 hr
Average speed = 415 km/hr
Therefore, the driver must achieve an average speed of 415 km/hr for the final two laps in order to qualify for the race.