What is the largest positive six digit number using 1, 2,4,5,7,8 only once that is divisible by 11.

Question

each digit can be used only once

Answer 1

To see if a number is divisible by 11, you alternately add and subtract its digits. If the sum is divisible by 11, then so is the large number. For example:

134568 = 1 - 3 + 4 - 5 + 6 - 8 = -5, so 134568 is not divisible by 11.

291654 = 2 - 9 + 1 - 6 + 5 - 4 = -11, so 291654 is divisible by 11.

 

Can you arrange the digits you're given to make this work out?