Six baskets of eggs. Sell one, and the rest splits exactly 2:1 chicken to duck
A trader has six baskets of eggs, holding 5, 6, 12, 14, 23 and 29 eggs. Every basket is entirely one type: chicken eggs or duck eggs. 'If I sell this one basket,' he says, pointing at one of them, 'I'll be left with exactly twice as many chicken eggs as duck eggs.' Which basket is he selling?
Reveal the answer
The 29-egg basket. The remaining five baskets total 60 eggs, which splits into 40 chicken and 20 duck — and 23+12+5 does equal 40, while 14+6 equals 20. No other basket lets the rest divide into a clean 2:1 split by whole baskets. The puzzle appears in Yakov Perelman's Figures for Fun as an exercise in testing every case systematically rather than guessing.
— Yakov Perelman, Mathematics Can Be Fun (Figures for Fun) — Part One, Puzzle 97