Divisibility by 11

Alternate the digits + and −. If the total is 0 or ±11, it divides by 11.

Is 2728 div by 11? = Yes

Each place leaves +1 or −1 against 11, and the sign flips every step left.

So tag the digits + and − from the right: 8 − 2 + 7 − 2 = 11.

The total is itself a multiple of 11, so 2728 divides exactly: 11 × 248.

Your turn

Three to try in your head — tap what you get.

10472 div by 11?

5219 div by 11?

4855 div by 11?