Hunting a number with clues
Think of a secret two-digit number. One clue can cross out many numbers.
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Step 1 of 4
- Numbers that could be the answer: 18, 27, 45, 52, 63, 90.
- Clue 1: digits add to 9. Cross out 52.
- Clue 2: greater than 50. Cross out 18, 27, 45.
- Clue 3: less than 70. Cross out 90. Answer: 63.
The rule
A clue is a fact about the secret number. A clue crosses out every number that does not fit it. Add clues until one number is left.
Check each number against the clues. The answer must fit every clue.
Example
Clues: the digit sum is 9. The number is above 50 and below 70. Look at 51 to 69. Digits add to 9 only in 54 and 63. 5 + 4 = 9 and 6 + 3 = 9. A fourth clue says the ones digit is 3. The ones digit is the last digit. That leaves 63.