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3 and 4-digit numbers (Posted on 2017-07-17) Difficulty: 2 of 5
Consider the number 4808
Notice: 4^2+8^2=80
i.e. the sum of the squares of this number's first and last digits equals the number obtained when the first and last digits are erased.

How many numbers with such feature exist below 10000?

Clearly, no leading zeroes.

See The Solution Submitted by Ady TZIDON    
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Solution re(3): Just counting (spoiler) | Comment 4 of 6 |
(In reply to re(2): Just counting (spoiler) by Steve Herman)

Not so.

Each of the seven generates 2 numbers:  one of 3 digits
 and one of 4 (see the title)  - both are below 10000:
 e.g. 21==> 251 & 2051;  30==>390 &3090
83 is the correct answer.

  Posted by Ady TZIDON on 2017-07-17 14:16:13
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