A balance-scale puzzle from the ATC – the Actuarial Turf Club
The ATC were running a race with 12 horses, each carrying a saddlebag of identical assigned weight. On the eve of the race, someone swapped one bag’s weight – either heavier or lighter than the rest. The digital scale broke, leaving only a classic balance scale, which compares equal numbers of bags on each side.
With just three weighings, the stewards (they were all actuaries) could identify the tampered saddlebag and decide whether it was heavy or light. Can you work out how?
S1
S2
S3
S4
S5
S6
S7
S8
S9
S10
S11
S12
