Answer Key: Prime and Composite Numbers:



Answer Key: Prime and Composite Numbers One:

Write all the factors for the numbers below and circle whether they are prime or composite numbers (the first one is done for you):

|3 | 1  | 3  |  |  |  |  | Prime  | Composite  |

|5 | 1  | 5  |  |  |  |  | Prime  | Composite  |

|9 | 1  | 3  | 9  |  |  |  | Prime  | Composite  |

|14 | 1  | 2  | 7  | 14  |  |  | Prime  | Composite  |

|21 | 1  | 3  | 7  | 21  |  |  | Prime  | Composite  |

|31 | 1  | 31  |  |  |  |  | Prime  | Composite  |

|35 | 1  | 5  | 7  | 35  |  |  | Prime  | Composite  |

|43 | 1  | 43  |  |  |  |  | Prime  | Composite  |

|51 | 1  | 3  | 17  | 51  |  |  | Prime  | Composite  |

|59 | 1  | 59  |  |  |  |  | Prime  | Composite  |

Answer Key: Prime and Composite Numbers Practice Two:

Write all the factors for the numbers below and circle whether they are prime or composite numbers (the first one is done for you):

|3 | 1  | 3  |  |  |  |  | Prime  | Composite  |

|7 | 1  | 7  |  |  |  |  | Prime  | Composite  |

|9 | 1  | 3  | 9  |  |  |  | Prime  | Composite  |

|16 | 1  | 2  | 4  | 8  | 16  |  | Prime  | Composite  |

|18 | 1  | 2  | 3  | 6  | 9  | 18  | Prime  | Composite  |

|23 | 1  | 23  |  |  |  |  | Prime  | Composite  |

|33 | 1  | 3  | 11  | 33  |  |  | Prime  | Composite  |

|41 | 1  | 41  |  |  |  |  | Prime  | Composite  |

|63 | 1  | 3  | 7  | 9  | 21  | 63  | Prime  | Composite  |

|97 | 1  | 97  |  |  |  |  | Prime  | Composite |

Answer Key: Sample Word Problems:

1. There are no equal ways to sort the books evenly because 23 is a prime number. One group of 23 is the only even way to split them with no remainders.

2. You can arrange them into 2 groups of 14 and 4 groups of 7. You could also arrange them into 14 groups of 2 and 7 groups of 4. Clearly, 28 is a composite number.

3. 53 is a prime number, so there is not a way to split them evenly and not throw one away.

4. The farmer can plant the corn in 2 rows of 18 or 18 rows of 2. He can plant it in 3 rows of 12 or 12 rows of 3. He can plant it in 4 rows of 9 or 9 rows of 4. He could plant it in 6 rows of 6. He could also plant it in 1 row of 36. 36 is a composite number.

5. You can group them 2 ways: One group of 25 or 5 groups of 5. Any other way would not allow the teams to be even. 25 is a composite number.

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