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# how to use a table

In this entry, how to use a table to multiply numbers will be explained and illustrated with examples. The general rule is as follows:

Suppose you want to multiply two numbers. Find the first number in the very first column. Follow the row in which this number appears until you land in the column which is labelled with the second number on top. The number on which you land is your answer.

Let us illustrate with an example. To keep things simple, we will use a 5 by 5 multiplication table

$\times$ | 1 | 2 | 3 | 4 | 5 |
---|---|---|---|---|---|

1 | 1 | 2 | 3 | 4 | 5 |

2 | 2 | 4 | 6 | 8 | 10 |

3 | 3 | 6 | 9 | 12 | 15 |

4 | 4 | 8 | 12 | 16 | 20 |

5 | 5 | 10 | 15 | 20 | 25 |

Suppose we want to figure out $3\times 4$. We first find the row which starts with “3”. That row is highlighted below:

$\times$ | 1 | 2 | 3 | 4 | 5 |
---|---|---|---|---|---|

1 | 1 | 2 | 3 | 4 | 5 |

2 | 2 | 4 | 6 | 8 | 10 |

3 | 3 | 6 | 9 | 12 | 15 |

4 | 4 | 8 | 12 | 16 | 20 |

5 | 5 | 10 | 15 | 20 | 25 |

Next we follow this row until we find the column which has “4” on top. This column is highlighted below:

$\times$ | 1 | 2 | 3 | 4 | 5 |
---|---|---|---|---|---|

1 | 1 | 2 | 3 | 4 | 5 |

2 | 2 | 4 | 6 | 8 | 10 |

3 | 3 | 6 | 9 | 12 | 15 |

4 | 4 | 8 | 12 | 16 | 20 |

5 | 5 | 10 | 15 | 20 | 25 |

Note that “12” appears where the highlighted row and the highlighted column cross. (For convenience, it has been underlined.) Therefore, we found that $3\times 4=12$.

## Mathematics Subject Classification

11B25*no label found*

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