Arithmetic for the Grandchildren


The numbers between the vertical lines are of two kinds. The ones that are not set equal to other numbers are called prime numbers. They are printed in bold. The others are each set equal to two other numbers multiplied by each other. The x indicates multiplication. A number set equal to the multiplication of numbers is called a product.

The listing shows that 54 is the product of 6 and 9 (54 = 6 x 9). There is more than one way to get 54. It is also equal to 3 x 18. These are the products that you should learn first. Learning the ones at the start of the list before learning the later ones is also a good idea, because knowing them allows you to understand the products that come later.

2 | 3 | 4 = 2 x 2 | 5 | 6 = 2 x 3 | 7 | 8 = 2 x 4 | 9 = 3 x 3 | 10 = 2 x 5 | 11 | 12 = 2 x 6| 13 | 14 = 2 x 7

15 = 3 x 5 | 16 = 2 x 8 | 17 | 18 = 2 x 9 | 19 | 20 = 2 x 10 | 21 = 3 x 7 | 22 = 2 x 11 | 23 | 24 = 2 x 12 |

25 = 5 x 5 | 26 = 2 x 13 | 27 = 3 x 9 | 28 = 2 x 14 | 29 | 30 = 2 x 15 | 31 | 32 = 2 x 16 | 33 = 3 x 11 |

34 = 2 = 17 | 35 = 5 x 7 | 36 = 4 x 9 | 37 | 38 = 2 x 19 | 39 = 3 x 13 | 40 = 4 x 10 | 41 | 42 = 6 x 7 |

43 | 44 = 4 x 11| 45 = 5 x 9 | 46 = 2 x 23 | 47 | 48 = 6 x 8 | 49 = 7 x 7 | 50 = 5 x 10 | 51 = 3 x 17 |

52 = 4 x 13 | 53 | 54 = 6 x 9 | 55 = 5 x 11 | 56 = 7 x 8 | 57 = 3 x 19 | 58 = 2 x 29 | 59 | 60 = 6 x 10 |

61 | 62 = 2 x 31 | 63 = 7 x 9 | 64 = 8 x 8 | 65 = 5 x 13 | 66 = 6 x 11 | 67 | 68 = 4 x 17 | 69 = 3 x 23 |

70 = 7 x 10 | 71 | 72 =8 x 9 | 73 | 74 = 2 x 37 | 75 = 3 x 25 | 76 = 4 x 19 | 77 = 7 x 11 |78 = 6 x 13 |

79 | 80 = 8 x 10 | 81 = 9 x 9 | 82 = 2 x 41 | 83 | 84 = 4 x 21 | 85 = 5 x 17 | 86 = 2 x 43 | 87 = 3 x 29 |

88 = 8 x 11 | 89 | 90 = 9 x 10 | 91 = 7 x 13 | 92 = 4 x 23 | 93 = 3 x 31 | 94 = 2 x 47 | 95 = 5 x 19 |

96 = 3 x 32 | 97 | 98 = 2 x 49 | 99 = 9 x 11 | 100 = 10 x 10 |

Counting by two (2, 4 6, 8, 10) is not the only way to count by steps. Once you get familiar with the numbers, you might try counting by eleven, of any other number. These exercises will give you a fast way to become skilled in arithmetic.