Apologies for not posting the solution last week, I was traveling on vacation on the weekend.
This was a relatively difficult puzzle, but I was encouraged to see the number of people who responded, most of them with correct answers. Anirudh & Anvi from Singapore, Alok Kuchlous from Bangalore, Siddhansh (IIT Kanpur) and Swati, a colleague at Helion, sent the correct answers. Prakash Prakash sent an “almost correct” answer. Well done all!
Reproducing the answer from Alok Kuchlous, and also attaching a link to the video if you would like to use that:
It can be done in 7 races.
Divide into 5 groups and race. (5 races)
Let rankings be:
A1, A2, A3, A4, A5; B1..B5; C1..C5; D1..D5; E1..E5
Race: A1, B1, C1, D1, E1. (6th race)
let the order be same as above i.e. A1 to E1. So first is A1.
2nd and 3rd could be:
So you need to only race A2, A3, B1, B2, C1. (7th race)
Pick the top two.
Hope you enjoyed the puzzle.