The greatest common divisor (GCD) of two numbers, say 12  and 8 , is the greatest number (in this case, 4) that divides them without a...

This intriguing puzzle, which even Harvard students got wrong, highlights how two modes of thinking, fast and slow, affect our decisions

Puzzle.  Three students, Peter, James, and Emma, went out to celebrate their exams. Peter bought five beer bottles, each costing £3, whereas James bought three. At the night's end, Emma handed Peter £7 and James £1, saying they were even. Peter happily accepted, but James felt he was shorted. Who cheated in the math exam? Three students went out to celebrate their exams . Solution.  Peter and James contributed 5 to 3 but were refunded 7 to 1, which may seem unfair. However,