If the amount you are out of balance is divisible by 2, the error may be an entry that has been posted backwards. That is to say something that should be a credit is posted as a debit or vice versa. To find this error, divide your error by 2 and look for an entry of the resulting amount. Then make sure it was posted in the correct direction.
A transposition is where two digits of a number have been listed in reverse order. For example 290 is listed as 920. The 2 and 9 are transposed causing an error of 630 (920-290). If the balance error is divisible by 9, a transposition is likely.
You can tell how far apart the digits transposed are by how many times the error is divisible by 9. In the example above the error (630) is divisible by 9 70 times, so we know that the digits transposed have a difference of 7, such as 1 and 8. 2 and 9. or 0 and 7. In our case, it is 2 and 9.
Since the error is divisible by 9 70 times and not 7 or 700, we would know that the digits transposed are in the hundreds and tens digit positions.