Problem
First name
Alisha, Ben, Callum, Megan and Tia
School
Beechwood Primary School, Leeds
Country
Age
10
We worked out that all the totals can be divided by 11 with no remainder.
In the ISBN code
0-74755?-19-1
the question mark must be replaced by the number 8 because this is the only one digit number that makes a total which is exactly divisible by 11. See the table below.
Multiplier 1 2 3 4 5 6 7 8 9 10 Total:
ISBN Number 0 7 4 7 5 5 8 1 9 1
Product 0 14 12 28 25 30 56 8 81 10 264 = 24 x 11
We think that the purpose of this property of ISBN codes is to make sure that every ISBN code is valid and can be used to identify the book.