Question

Two cars start to drive around a 2 km track at the same time. car x make one lap every 80 seconds while car y makes one lap every 60 s

(a)how long will it take for the cars to be at their starting point again? give your answer in minutes.
(b)how long will it take to the faster car to be ahead by 15 laps? give your answer in hours.

Answer 1

20 minutes

Explanation:

Both will meet again at start point after LCM(60,80) seconds.

That is 240 seconds.

in time slower car completes one lap, faster one covers 1 +20/80 lap, that is 1.25 laps. After 20 laps faster by slower car car will be 5 laps ahead, time =20*60 = 1200s = 20 minutes