A and B run a 5 km race on a round course of 400 m. If their speed are in the ratio 5 : 4, the number of times, the winner passes the other is

Ratio of speed of A and B = 5 : 4
When A runs 500 m, B runs 400 m
A will pass B every time when the distance between them is 400 m
A will cover = $$\frac{{400}}{{\left( {500 - 400} \right)}}$$   = 2000 m to overtake B each time
Number of time = $$\frac{{5000}}{{2000}}$$  = 2.5 ≈ 2 times (because .5 time is not possible)