A traveler needs to cross a river with a cat, a mouse, and a wheel of cheese using a boat that can only carry the traveler and one item at a time. Left alone, the cat will eat the mouse, and the mouse will eat the cheese. What is the minimum total number of one-way river trips needed to get all three safely across?
7 trips
Trip 1: Take mouse across. Trip 2: Return alone. Trip 3: Take cat across. Trip 4: Return with mouse. Trip 5: Take cheese across. Trip 6: Return alone. Trip 7: Take mouse across. Total = 7 trips.
About this riddle
Logic riddles give you a few facts and ask what must be true. List what you know, cross out what cannot be, and see what is left.
Difficulty: Medium. More like this: Logic riddles with answers or try Einstein's Logic Grid for a different kind of puzzle.
More logic riddles
I am a two-digit number. My tens digit is three times my units digit. If you reverse my digits, the new number is 36 less than my original value. What number am I?
A line goes: pumpkin, dinner roll, pumpkin, dinner roll, pumpkin. What comes next?
Five numbered lockers (1 to 5) hold five items: Ball, Train, Car, Doll, Robot. Locker 1 has the Ball. Locker 4 has the Doll. The Car is immediately to the left of the Doll. The Robot is in an odd-numbered locker. Which locker holds the Robot?
Five coins are placed on a table in a straight line: A, B, C, D, and E. Exactly two coins show heads. Coin A and Coin E show the same face. Coin B and Coin D show different faces. Coin C shows tails. If Coin A shows heads, which two coins show heads?
On a remote island, inhabitants are either Knights (who always tell the truth) or Knaves (who always lie). You meet two inhabitants, X and Y. X says: 'At least one of us is a Knave.' What are X and Y?
A teacher places three shapes on the board: a red circle, a blue square, and a green triangle. She gives three clues about her secret shape: 1. It has straight sides. 2. It is not red. 3. It does not have three sides. Which shape did she select?