Posted by **monica** on Sunday, August 24, 2008 at 10:06am.

To qualify for the race, each driver must complete 2 laps of the track at an average speed of 100 mi/h. Benjamin averages only 75 mi/h on his first lap. How fast must he go on his second lap to qulify for the race?

- math -
**Reiny**, Sunday, August 24, 2008 at 1:09pm
let the distance around the track be d km

so the time needed to qualify is 2d/100

his time for the first lap is d/75 hours

let his speed for the second lap be r km/h

so the time for his second lap is d/r hours

total time = d/75 + d/r = (dr+75d)/75

then (dr+75d)/75 = 2d/100

divide both sides by d

(r+75)/75 = 2/100

you finish it, let me know what you got

- math -
**monica**, Sunday, August 24, 2008 at 1:26pm
i got 3675, but that doesn't make any sense, he has to go 3675 mph?

- math -
**drwls**, Sunday, August 24, 2008 at 5:18pm
I believe Reiny meant to write

d/75 + d/r = (dr + 75 d)/(75 r)

=================================

d/75 + d/r = 2d/100

1/r = 2/100 - 1/75 = 6/300 - 4/300 = 1/150

r = 150

## Answer this Question

## Related Questions

- physics - to qualify for a race, a car must average 350 km/hr for four laps. If ...
- Physics - To qualify for the finals in a racing event, a race car must achieve ...
- Physics - In order to qualify for the finals in a racing event, a race car must ...
- physics - In order to qualify for the finals in a racing event, a race car must ...
- physic - 1) if you live 10.0 km from your school and the bus takes 0.53 h to ...
- physic - In order to qualify for the finals in an race, a runner must achieve an...
- physics help please! - A race car is one lap behind the lead race car when the ...
- phsyics - A car races on a circular track of radius r. (a) Write an equation ...
- physics - At the Indianapolis 500 time trials, each car makes four consecutive ...
- physics - A runner training for a race times 400 meter laps. Lap 1 60sec, Lap 2 ...

More Related Questions