Brain teasers
Logic puzzles, riddles, and number traps from Think Fanny. Solve first, then reveal the answer on each page — or build a weekly rhythm with the logic practice guide.
Three switches, one bulb
A classic room puzzle with three switches and one light. Find the method that always works.
Fox, goose, and grain
Get a fox, a goose, and a sack of grain across the river without anyone eating lunch early.
Odd one out: 3, 5, 7, 9, 11, 13
One number does not belong with the primes in this short list.
When are clock hands at right angles?
How many times do the hour and minute hands form a right angle between noon and midnight?
Two coins add up to 30 cents
A short money riddle that trips people who assume both coins are normal.
Blue eyes, brown eyes, and a ferry
A famous induction puzzle. Why does the guru's sentence start a countdown?
Nine balls, one heavy, two weighings
Find the heavy ball with a balance scale and only two uses.
The missing dollar
Three guests, a hotel refund, and a story that does not add up. Where is the flaw?
What has a neck but no head?
A clean one-liner riddle with a concrete answer.
How many letters in the month after May?
A wordy calendar teaser that rewards careful reading.
The man who only rides to floor 10
A short man takes the elevator. Why does his routine change on rainy days?
Three wise people, red hats
They can see others' hats. Who figures out their color, and how?
Split $47 three ways
A mental-math money split with a one-cent catch.
What is always in front of you but cannot be seen?
A one-line riddle for a quick win.
Prisoners in a line with hats
They hear one letter, then each must guess. How do they save almost everyone?
Move one match: XI = III + III
A matchstick Roman-numeral equation with one legal move.