Puzzles
Buy a pig, sell it, buy it back, sell it again — profit or loss?
A farmer buys a pig for $60, sells it for $70, buys it back for $80, then sells it again for $90. Without adding it up on paper, what's your gut sense: did the farmer come out ahead, break even, or lose money — and by how much?
Reveal the answer
A profit of $20. It's easy to only weigh the final $90 sale against the $80 cost and guess $10, but there are two separate buy-sell cycles: $70−$60=$10, then $90−$80=$10, for $20 total. It's one of the items added to Shane Frederick's 2005 Cognitive Reflection Test to catch people answering from gut instinct rather than working it through.