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Find the number of positive integers that satisfy both the following conditions:

Each digit is a 1 or a 3

The sum of the digits is 12

 Nov 25, 2023
 #1
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There is only one way to make 12 with a single digit, namely with 3. There are 2 ways to make 12 with 2 digits: 11 and 31. There are 3 ways to make 12 with 3 digits: 111, 131, and 311. Finally, there are 3 ways to make 12 with 4 digits: 1131, 1331, and 3311. Thus, the total number of positive integers that satisfy the given conditions is 1+2+3+3=9​.

 Nov 25, 2023
 #2
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sorry, that's wrong. The problem is asking for any way to make it 12, and i dont think that your answers match that. It asks how many possibilities are there that could work.

Icebulb2  Nov 25, 2023

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