What 5-digit number am I thinking of?
It has two prime digits.
Digit 3 is the highest digit.
Digit 2 is the lowest digit.
Digit 1 is higher than the sum of digits 4 and 5.
Digit 5 is half of digit 4.
Digit 1 is one smaller than digit 3.
Digit 5 is between digit 2 and digit 1
The digit 0 doesn't appear, and there are no duplicates. Don't forget that 1 isn't prime, the prime numbers start with 2, 3, 5...
Puzzle Copyright © Kevin Stone
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Hint
What can digits 4 and 5 be?
Answer
71842.
Reasoning
The number can be represented as:
- - - - -
By (5), Digit 5 is half of Digit 4, so we have four possibilities:
- - - 2 1
- - - 4 2
- - - 6 3
- - - 8 4
By (4), Digit 1 is higher than the sum of Digit 4 and Digit 5, so we can eliminate two possibilities, leaving:
- - - 2 1
- - - 4 2
By (7), Digit 5 is between Digit 2 and Digit 1, so we can eliminate - - - 2 1, leaving:
- - - 4 2
By (4), Digit 1 must be higher than the sum of Digit 4 and Digit 5, so we have three possibilities:
7 - - 4 2
8 - - 4 2
9 - - 4 2
By (6), Digit 1 is 1 smaller than Digit 3 we can eliminate 9 - - 4 2, and fill in Digit 3, leaving:
7 - 8 4 2
8 - 9 4 2
By (3), Digit 2 is the lowest digit, and must be 1:
7 1 8 4 2
8 1 9 4 2
By (1), the only possibility is:
7 1 8 4 2
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