1234567 is not divisible by 11. But we can rearrange its digits to 1537426 so that it is divisible by 11.
Can we also rearrange the digits of the number 12345678 so that the resultant number is again divisible by 11?
This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try
refreshing the page, (b) enabling javascript if it is disabled on your browser and,
finally, (c)
loading the
non-javascript version of this page
. We're sorry about the hassle.
The rule for divisibility by 1 1 is that the alternating sum of an integer be divisible by 1 1 . As an example, the alternating sum of 8 2 3 9 is 8 − 2 + 3 − 9 = 0 , which is divisible by 1 1 and thus so is 8 2 3 9 , (indeed 8 2 3 9 = 1 1 × 7 4 9 ). Now the sum of the digits 1 through 8 is 3 6 , so one way we can create a number that is divisible by 1 1 is to choose 4 digits that sum to 1 8 , leaving the remaining 4 digits to sum to 1 8 as well, and then alternating these two sets of digits. So choosing 1 , 4 , 5 , 8 as one 4-digit set, we know by the alternating-sum rule that 1 2 4 3 5 6 8 7 will be divisible by 1 1 , since 1 − 2 + 4 − 3 + 5 − 6 + 8 − 7 = 0 . The answer is therefore Yes .
Note: 1 2 4 3 5 6 8 7 = 1 1 × 1 1 3 0 5 1 7 . A potential follow-up question would be to find the probability that a random permutation of 1 2 3 4 5 6 7 8 is divisible by 1 1 .