Answer:
18 minutes
Explanation:
Runner A: 5 km/h
Runner B: 8 km/h
Runner C: 15 km/h
speed = distance/time
time × speed = distance
time = distance/time
Runner A:
time = 500 m / (5 km/h) = 0.5 km / (5 km/h) = 0.1 h = 6 minutes
Runner B:
time = 500 m /(8 km/h) = 0.5 km / (8 km/h) = 0.06 h = 3.6 minutes
Runner C:
time = 500 m / (15 km/h) = 0.5 km / (15 km/h) = 0.0333 h = 2 minutes
Runners A, B, and C take 6 minutes, 3.6 minutes, and 2 minutes, respectively, to run 1 lap around the track.
Now we need the least common multiple of 6, 3.6, and 2.
Start with multiples of 6:
6
6/3.6 = 1.666 does not work.
12
12/3.6 = 3.333 does not work.
18
18/3.6 = 5 works
18 is a multiple of 6, 3.6, and 2.
Answer: 18 minutes