In 87659_21 what is the least number which can be filled in blank so that the number is divisible by 11.

Question: In 87659_21 what is the least number which can be filled in blank so that the number is divisible by 11.

Solution:
Divisibility rule of 11:
If the sum of digits at odd and even places are equal or differ by a number divisible by 11, then the number is also divisible by 11.
Let the number of blank place be x
Now,
(8 + 6 + 9 + 2) - (7 + 5 + x + 1) = 0 or 11
⇒ 25 - 13 - x = 0 or 11
⇒ 12 - x = 0 or 11

12 - x = 0
∴ x = 12

Or
12 - x = 11
⇒ x = 12 - 11
∴ x = 1