Our expert team of math educators and enthusiasts has spent over 40 years developing and refining the most powerful teaching methods and materials into our comprehensive, industry-leading Mathnasium Method™.

These “Ask Education” features are a way for our Education team members to share their knowledge and love of math with our curious readers and fans.

To test if a number is divisible by 11, follow the general rule: the difference of the sum of alternating digits can be divided by 11.

To determine if the number 2,728 is divisible by 11, find the difference of the sum of alternating digits.

One way to test if a three-digit number is divisible by 11 is to follow the 3-digit rule: the sum of the first and last digits equals the middle digit.

To determine if the number 792 is divisible by 11, we find the sum of seven and two.