perplexus.info :: Numbers : 3 and 4-digit numbers

3 and 4-digit numbers (Posted on 2017-07-17)

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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re(3): Just counting (spoiler)

| Comment 5 of 7 |

(In reply to re(2): Just counting (spoiler) by Steve Herman)

Yes of course 76 + 7 = 83. I've edited my response to correct that type.

And as Ady has pointed out, those 7 outer two digits produce 14, rather than 7 inner digits, one with and one without a leading zero.

Posted by Charlie on 2017-07-17 21:59:59

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