Computer Science · May / June 2016 · Paper 11 · Question 9
2210
As printed in the paper
The question as text
Check digits are used to ensure the accuracy of entered data. A 7-digit number has an extra digit on the right, called the check digit. digit position: 1 2 3 4 5 6 7 8 digit: – – – – – – – – check digit The check digit is calculated as follows: • each digit in the number is multiplied by its digit position • the seven results are then added together • this total is divided by 11 • the remainder gives the check digit (if the remainder = 10, the check digit is X)
Read automatically from the paper; the printed page above is exact.
Show the answer and mark scheme
9(a)[2]
1 mark for correct check digit and 1 mark for showing the calculation (4 × 1) + (2 × 2) + (4 × 3) + (1 × 4) + (5 × 5) + (0 × 6) + (8 × 7) = 4 + 4 + 12 + 4 + 25 + 0 + 56 = 105 105/11 = 9 remainder 6 check digit is: 6 [2]
9(b)[3]
incorrect check digit [1]
– check digit should be 1 – (3*1) + (2*2) + (4*3) + (0*4) + (0*5) + (4*6) + (5*7) // 3 + 4 + 12 + 0 + 0 + 24 + 35 // Total = 78 – 78/11 gives 7 remainder 1 [2]
1 mark for any correct line of working
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