SOLUTION: I have tried this one several times and can not get the answer. The stopping distance d of a car after the brakes are applied varies directly as the square of the speed r. If a car

Algebra ->  Equations -> SOLUTION: I have tried this one several times and can not get the answer. The stopping distance d of a car after the brakes are applied varies directly as the square of the speed r. If a car      Log On


   

Question 320142: I have tried this one several times and can not get the answer. The stopping distance d of a car after the brakes are applied varies directly as the square of the speed r. If a car travelling 70 mph can stop in 270 ft, how many feet will it take the same car to stop when it is travelling 30 mph?
Answer by ankor@dixie-net.com(22740) About Me  (Show Source):
You can put this solution on YOUR website!
The stopping distance d of a car after the brakes are applied varies directly as
the square of the speed r.
If a car traveling 70 mph can stop in 270 ft, how many feet will it take the
same car to stop when it is traveling 30 mph.
:
Use a ratio equation, find d for 30 mph:
70%5E2%2F30%5E2 = 270%2Fd
:
4900%2F900 = 270%2Fd
cross multiply
4900d = 900 * 270
:
4900d = 243000
d = 243000%2F4900
d = 49.6 ft, stopping distance at 30 mph