Question

a ferrari and a porsche begin a race with a moving start and each car moves with constant speed. the ferrari laps overtakes the porsche after the porsche has completed 9 laps. if the speed of the ferrari had been 10 km/hr less the porsche would have traveled 18 laps before being overtaken. if needed a lap=2 km. what were the speeds of the two cars?

Answer 1

Let
P = speed of Porsche
F = speed of Ferrari

The Ferrari makes 10 laps while the Porsche completed 9.
Thus,
20/F = 18/P
F = (20/18)P
F = (10/9)P ....(1)

If the Ferrari had been 10 km/h less, then it would have done 19 laps in the time the Porsche had done 18. Therefore
38/(F-10) = 36/P
36(F-10) = 38P
36F = 38P + 360 (2)

Substitute (1) in (2) and solve for F and P.

Answer 2

where exactly did you get the 38 and 36 from in the 2nd portion of the question?

Answer 3

18 laps * 2 km =36 km
19 laps ....