Codebusters Test Codebusters Logical Puzzles and Riddles 2 — Questions and Answers
Question 1: In a cryptarithmetic puzzle, SEND + MORE = MONEY. What digit does M represent?
- 0
- 1 (Correct answer)
- 2
- 9
Correct answer: 1
M = 1 because MONEY is a 5-digit sum of two 4-digit numbers, so the carry into the ten-thousands place can only be 1.
Question 2: A self-referential sentence reads: 'This sentence has ___ letters.' Which number correctly completes it?
- 27
- 30 (Correct answer)
- 31
- 32
Correct answer: 30
Writing out 'thirty' gives exactly 30 letters in the full sentence, making it self-referentially true.
Question 3: If A=1, B=2, ... Z=26 in a simple substitution, what is the product of the values of the letters in 'CAB'?
- 6 (Correct answer)
- 8
- 12
- 24
Correct answer: 6
C=3, A=1, B=2; 3×1×2 = 6.
Question 4: Three logicians (A, B, C) each see the others' hat colors but not their own. A says 'I don't know.' B says 'I don't know.' C immediately says 'I know.' What logical principle does C use?
- Common knowledge elimination (Correct answer)
- Bayes' theorem
- Direct deduction
- Random guess
Correct answer: Common knowledge elimination
C uses common knowledge elimination: A's and B's ignorance rules out scenarios where one color is unique, letting C deduce their own hat.
Question 5: A number is encoded so that each digit D becomes (D + 5) mod 10. What does encoded digit 3 decode to?
- 2
- 7
- 8 (Correct answer)
- 3
Correct answer: 8
To decode, reverse the encoding: (3 − 5 + 10) mod 10 = 8.
Question 6: In a logic grid puzzle, five items must be matched to five slots with no repeats. How many total arrangements are possible before applying any constraints?
- 25
- 120 (Correct answer)
- 720
- 3125
Correct answer: 120
The number of permutations of 5 items is 5! = 120.
Question 7: A riddle states: 'I have cities but no houses; mountains but no trees; water but no fish. What am I?' What is the answer?
- A dream
- A map (Correct answer)
- A painting
- A mirror
Correct answer: A map
A map has symbols for cities, mountains, and water without the physical objects themselves.
Codebusters Test Codebusters Logical Puzzles and Riddles 2
In a cryptarithmetic puzzle, SEND + MORE = MONEY.
What digit does M represent?