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ISBN Numbers

ISBN Numbers. Every book published has an ISBN number ISBN is the International Standard Book Number The last digit or character of the number is called the check digit. A check digit means that a computer can check if the code for the book is valid How does the computer check?. Answer ……….

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ISBN Numbers

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  1. ISBN Numbers

  2. Every book published has an ISBN number • ISBN is the International Standard Book Number • The last digit or character of the number is called the check digit

  3. A check digit means that a computer can check if the code for the book is valid • How does the computer check?

  4. Answer ………. • By using multiplication tables and then multiples of 11

  5. Write down the first 25 multiples of 11

  6. Do you notice a pattern?

  7. 11 22 33 44 55 66 77 88 99 110 121 132 143 154 165 176 187 198 209 220 231 242 253 264 275

  8. What is the 34th multiple of 11?

  9. 34 x 11 • Open out the 34 3…. 4 • Add the 3+4, insert the 7 in the middle • 374 • 34 x 11 = 374 • Is it magic? • Why does this work? Does it always work?

  10. How about 45 x 11 ? • 4……… 5 • 4+5 = 9 • 495 • So 45 x 11 = 495

  11. How about 65 x 11 ? • 6……..5 • 6 + 5 = 11 • 6115 • But 65 x 11 is not 6115 • 65 x 11 = 715 • What happens here? 6… 5 1 1 ____ 715

  12. Why does this work? • 27 x 11 is 10 x 27 = 270 + 1 x 27 = 27 11 x 27 = 297 Look what happens to the digits in the sum

  13. Calculate……… • 72 x 11 • 48 x 11 • 61 x 11

  14. What should be added to 456 so that it can be divided by 11 with no remainder? • What should be added to 285 to make it a multiple of 11?

  15. Back to ISBN numbers • What does ISBN stand for? • What is the last digit or character called? • What is this last check digit for? • How does the computer do this?????

  16. The book “Year 5 Solving Problems” has the ISBN number 0 7136 5448 1 • The last digit is the check digit, 1

  17. 0 7136 5448 1 • How the computer works out the 1…. 0 x 10 = 0 7 x 9 = 63 1 x 8 = 8 3 x 7 = 21 6 x 6 = 36 5 x 5 = 25 4 x 4 = 16 4 x 3 = 12 8 x 2 = 16 • Total 197 • What should be added to 197 to make it a multiple of 11? • Next multiple of 11 is 198, so add 1. This is the check digit.

  18. “Red Herrings and White Elephants”ISBN number 1 84358 129 #? • Find the check digit #

  19. 1 8 4 3 5 8 1 2 9

  20. 1 x 10 = 8 x 9 = 4 x 8 3 x 5 x 8 x 1 2 9

  21. 1 x 10 = 10 8 x 9 = 72 4 x 8 = 32 3 x 7 = 21 5 x 6 = 30 8 x 5 = 40 1 x 4 = 4 2 x 3 = 6 9 x 2 = 18 Total 233 Next multiple of 11? 242 Check digit must be 9

  22. Think about the possible check digits, what could they be? • 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10 • There is only one space for the check digit, so the 10 becomes Roman, X

  23. Find some books for yourself and calculate the check digit

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