Brainteasers

[Onyxmeth]

TruckOSaurus said:
There is a faster way.

I'll further my hint this way :

The 5 first races go like this :

1-2-3-4-5
6-7-8-9-10
11-12-13-14-15
16-17-18-19-20
21-22-23-24-25

To simplify, let's say they place according to their assigned number. We can eliminate 10 horses that way : 4-5-9-10-14-15-19-20-24-25.

I tried it that way too, thinking it would give me a shortcut, but I haven't found anything yet. I may have one lead I'll test out which may cut it to 10 races, but I can't imagine it being any less than 10.