5 puzzles from Shane Frederick, each explained in a minute and credited to the original work. Free on Savvy.
A bat and a ball cost $1.10 in total. The bat costs $1.00 more than the ball. How much does the ball cost? Answer fast — then check yourself.
— Shane Frederick, Cognitive Reflection and Decision Making
A patch of lily pads doubles in size every day. It takes 48 days to cover the entire lake. How long does it take to cover half the lake?
— Shane Frederick, Cognitive Reflection and Decision Making
If it takes 5 machines 5 minutes to make 5 widgets, how long would it take 100 machines to make 100 widgets?
— Shane Frederick, Cognitive Reflection and Decision Making
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 ahea…
— Shane Frederick (original test); extended by later researchers, Cognitive reflection test
Almost everyone's first answer is 10 cents. It feels obviously right, arrives instantly, and is wrong. Can you find the actual price of the ball, and see why your gut answer fails …
— Shane Frederick, Cognitive Reflection and Decision Making