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Challenge Response 138


5 digit number

We know that the fifth digit is half the fourth and a quarter of the third digit:
5th digit = a

The fourth digit is double the fifth:
4th digit = 2nd

The third digit is the quadruple of the fifth:
3rd digit = 4th
The third digit is half of the first and double of the fourth. We already know that:
3rd digit = 4th
4th digit = 2nd

So the first digit is double the third:
1st digit = 8a

The second digit is three times the fourth and has five units more than the fifth:
2nd digit = 3.2a = 6a
2nd digit = a + 5

Let's ride an equality. Knowing that a = 1, we can find the value of each digit:
1st digit = 8a = 8
2nd digit = 6a = 6
3rd digit = 4a = 4
4th digit = 2a = 2
5th digit = a = 1

The number sought is 86421.

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