You can also be fooled by logic. Take this puzzle: Three travelers stop at a hotel and ask the front desk clerk “If we stay in the same room, what will the price be?” The clerk says, It will be $30". (obviously this happened 40 years ago.) The travelers each hand the clerk a $10 bill. After they go to their room, the clerk remembers that there is a special going that night, and the room is actually $25. So, he gives five singles to the bell boy, and sends him up to the room to return the money. The bellboy realizes that the travelers will never know the difference, and he only give them $3 (one dollar to each traveler) and pockets the other two dollars. So, the travelers have paid $9 each. 3 x9 = 27; plus the $2 the bellboy kept equals $29. Where’s the other dollar?
Because the logic of this last equation feels correct, we fail to realize that the math is all wrong! By adding the $2 the bell boy kept to the $27 dollars the travelers paid, you are actually adding the $2 twice. It is already in the $27 amount. ($25 the clerk has, plus $2 the bell boy has.) The amount that is missing, and the one that would solve the missing dollar problem, is the $3 the travelers got back! $3 x $9 + $3 = 30. Feels wrong, but it is RIGHT!
Originally published at https://www.bogerard.com on August 27, 2019.
