Discrete math:
find the rule for determining when a number is divisible by 11.

Step-by-step explanation:

Divisibility rule when a number is divisible by 11:

Take the alternating sum of digits in a number read from left to right .If that is divisible by 11 then the the given number is divisible by 11.

It is a divisibility rule of 11.

Let 1342 is a number .The number is divisible by 11 or not

Alternating sum of digits  =1-3+4-2=0

The alternating sum of digits is divisible by 11 .

Therefore, the number 1342 is divisible by 11.

Let a number 2728

Alternating sum of digits = 2-7+2-8=-11.

The alternating sum of digits is divisible by 11 .

Therefore, the number 2728 is divisible by 11.