Find the sum of all three-digit numbers in the record of which only numbers 1 and 3 are included?

univerkov | September 5, 2021 | education

Find all three-digit numbers that contain 1 and 3.

The most obvious numbers are 111 and 333.

Then we take one three and shift it: 311, 131, 113.

Then one 1: 133, 313, 331.

There are no more numbers. We find the amount:

111 + 333 + 311 + 131 + 113 + 133 + 313 + 331 = 1776

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