We will be dealing with two-digit numbers non divisible by 11.
For each such number A there will exist another A’, a number created by inverting the digits of A so 45’=54, 87’=78.
Take for example 2 numbers 36 & 84: their product is the same as the product of those numbers inverted i.e. 63*48.

Find all the couples possessing such feature i.e. AB=(A')*(B').
Rem: to preserve conformity present the smallest number on the LHS of the equation - like 12*42=21*24.

There are 36 trivial cases with a=d, b=c, e.g. 12*21=21*12

Edited on May 23, 2024, 11:56 pm

Posted by broll on 2024-05-23 23:30:12