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jasen

How many spin-able numbers are there from 0 to 99999 ?

Question

0,1,2,5,8,11,69,96 are spin-able numbers.

We call a number is a spin-able number if :

When it is typed on a calculator, then spin the calculator 180 degree, the number is still the same number with the original number.

How many spin-able numbers are there from 0 to 99999 ?

This is a no-computer puzzle, only right answers with explanation will be accepted.

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3 answers to this question

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Spoiler

One-digit numbers: (5)
0, 1, 2, 5, 8

Two-digit numbers: (6)
11, 22, 55, 69, 88, 96

Three-digit numbers: (6 * 5 = 30)
- Any qualifying two-digit number with any qualifying one-digit number inserted

Four-digit numbers: (6 * 7 = 42)
- Any qualifying two-digit number with any qualifying two-digit number or 00 inserted

Five-digit numbers: (42 * 5 = 210)
- Any qualifying four-digit number with any qualifying one-digit number inserted

Total: 5 + 6 + 30 + 42 + 210 = 293

 

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10 hours ago, jasen said:

0,1,2,5,8,11,69,96 are spin-able numbers.

We call a number is a spin-able number if :

When it is typed on a calculator, then spin the calculator 180 degree, the number is still the same number with the original number.

How many spin-able numbers are there from 0 to 99999 ?

This is a no-computer puzzle, only right answers with explanation will be accepted.

nevermind

Edited by BMAD

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