6 6 1 2 + 2 -> Invert -> + 1 9 9 | On a calculator, the digits 0,1,2,5,6,8,9 can all be inverted and still
be readable as numbers. (6 and 9 become each other and all other digits
are unchanged. In the example at left, the entire column can be inverted
and the sum (the lowest row) is still valid. Can you find an example where at least one summand uses two or more different digits? All summands should have the same number of digits. Leading zeros are allowed, and you could use two or more summands (the example uses three.) |

Solution

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