**ISBN-13 Validity**

ISBN-13 is the official and modern version of book indexing internationally. This method has been phasing out ISBN-10 since 2007. Just like ISBN-10, the numbers are linked mathematically to a weight to validate the authenticity of a book.

It is very simple to validate an ISBN-13 number, as it is validated using a weighted number system of 1 and 3 repeating.

1,3,1,3,1,3…

To give an example, I will show an ISBN-13 number and explain the process.

978-1932698183

To start we need to remove the dashes and multiply each number by the weight. Here is a graph so you can visualize it easier.

9781932698183

9 | *1 | 9 |

7 | *3 | 21 |

8 | *1 | 8 |

1 | *3 | 3 |

9 | *1 | 9 |

3 | *3 | 9 |

2 | *1 | 2 |

6 | *3 | 18 |

9 | *1 | 9 |

8 | *3 | 24 |

1 | *1 | 1 |

8 | *3 | 24 |

3 | *1 | 3 |

Once you have all of the weights applied, add all of the numbers together.

9+21+8+3+9+9+2+18+9+24+1+24+3=

140

Once you have added all of the weighted numbers up, divide that number by 10. If the number is divisible by 10, then the ISBN-13 is valid!

140/10=

14

(This isn’t the only way to check for validity with an ISBN-10 number, but it is a quick way to identify the validity of the book!)

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Now, you translate the Groups with the grid provided!

Now that you know how to identify the validity of a book, you can now buy a book knowing how to identify it and how to make sure it is valid!