Given that the integer 5a6a7a8a9a can be divided by 11, find all integers satisfying this condition
Characteristics of numbers divisible by 11
Add a number from the right to the left, and then calculate the difference between the odd and even digits. If the difference is a multiple of 11 (including 0), then the original number must be divisible by 11
5+6+7+8+9=35
Because 35-5a has to be a multiple of 11
So when a = 7, 35-5a = 0 is a multiple of 11
So the integer is 7