UPSC 2016 CDS II Math Paper

The speeds of A and B are in the ratio 5 : 4. So, when A runs 5 rounds, B runs 4 rounds.
∴ A passes B each time A has run 5 rounds or 5 x 0.25 = 1.25 km
Now,1.25+1.25+1.25=3.75km
Thus, A passes B thrice in the race.