Two different digits from 1 to 9 are chosen randomly to form a 2-digit number. By reversing the order of
the digits, a second 2-digit number is formed. What is the probability that the sum of these two numbers will
be a multiple of the sum of the digits?

 May 24, 2021

What have you tried?

 May 24, 2021

I like this question, it is much easier than it looks



Let the first digit be x  and the second by y


You might find it a little easier to think of two different scenarios.  Though really this is not necessary.

1.  x+y <10

2. x+y >10



If you want to look in advance then just draw up a 9 by 9 grid, fill in the outcomes and see what happens.


Please let 'thedude...'   work it out for himself from here.

Melody  May 24, 2021
edited by Melody  May 24, 2021

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