Let an integer to be called an alter integer if it satisfies the conditions below.
When a certain one of its digits is deleted, the integer is reduced to one ninths of its original value.
The resulting integer is divisible again by 9.
Find the sum of all alter integers that are not divisible by 10.
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The digit that is deleted must be a 0 or a 9 , because the digit sum must be divisible by 9 both before and after the deletion.
If the digit is a 9 , the situation is that A = 1 0 k + 1 x + 9 ⋅ 1 0 k + y , where y < 1 0 k , and B = 1 0 k x + y is the post-deletion integer, which is 1 / 9 of A . So we get 9 ( 1 0 k x + y ) 8 y = 1 0 k + 1 x + 9 ⋅ 1 0 k + y = 9 ⋅ 1 0 k + 1 0 k x which is manifestly impossible, since the right side is less than 8 ⋅ 1 0 k .
If the digit is a 0 , we similarly get A = 1 0 k + 1 x + y , B = 1 0 k x + y , and 9 ( 1 0 k x + y ) 8 y = 1 0 k + 1 x + y = 1 0 k x Since y < 1 0 k , we must have x < 8 . So there are exactly 7 values of x to consider. In each case, note that y will be divisible by 5 , so we'll need y to be odd so that A is not divisible by 1 0 .
For x = 1 we get y = 1 0 k / 8 is an odd integer, so k = 3 , y = 1 2 5 , A = 1 0 1 2 5 , B = 1 1 2 5 .
For x = 2 we get y = 1 0 k / 4 is an odd integer, so k = 2 , y = 2 5 , A = 2 0 2 5 , B = 2 2 5 .
For x = 3 we get y = 3 ⋅ 1 0 k / 8 is an odd integer, so k = 3 , y = 3 7 5 , A = 3 0 3 7 5 , B = 3 3 7 5 .
For x = 4 we get y = 1 0 k / 2 is an odd integer, so k = 1 , y = 5 , A = 4 0 5 , B = 4 5 .
For x = 5 we get y = 5 ⋅ 1 0 k / 8 is an odd integer, so k = 3 , y = 6 2 5 , A = 5 0 6 2 5 , B = 5 6 2 5 .
For x = 6 we get y = 3 ⋅ 1 0 k / 4 is an odd integer, so k = 2 , y = 7 5 , A = 6 0 7 5 , B = 6 7 5 .
For x = 7 we get y = 7 ⋅ 1 0 k / 8 is an odd integer, so k = 3 , y = 8 7 5 , A = 7 0 8 7 5 , B = 7 8 7 5 .
The sum of all the A 's is 1 7 0 5 0 5 .