Problem 13 · 2018 Math Kangaroo
Hard
Logic & Word Problems
casework
A lion hides in one of three rooms. The note on room 1 reads “The lion is not here.” The note on room 2 reads “The lion is here.” The note on room 3 reads “2 + 3 = 5.” Exactly one of the three notes is true. In which room is the lion?
Show answer
Answer: A — Room 1
Show hints
Hint 1 of 2
Notice the note on door 3 (2 + 3 = 5) is simply a true statement on its own.
Still stuck? Show hint 2 →
Hint 2 of 2
Since exactly one note is true, that forces the other two to be false; read off where the lion must be.
Show solution
Approach: use the always-true note to fix the count
- The note on room 3 says 2 + 3 = 5, which is true by itself.
- Exactly one note is true, so room 3's note is the true one and the other two are false.
- 'The lion is not here' on room 1 being false means the lion IS in room 1; 'the lion is here' on room 2 being false agrees.
- The lion is in Room 1.
Mark:
· log in to save