When A reaches the finishing line B is 50m behind A and C is 40m behind B.
This means that C is 50+40 m=90m behind A when A finishes the race.

The time required for the three participants in the above race is same.let it be t.


let x,y,z be the speeds of A,B,C respectively.

so by the time formula:


in .5km race the speeds of the three participants will be the same.

so dividing the eqn1 by 2 we get:


so in .5km race when A finishes the race C has covered 455m.

so he is behind A by (500-455)m

so A beats C by 45 m in .5km  race