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Grade
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Date
Questions20
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1

Find the GCF of 12, 15 and 18

2

Find the GCF of 8, 10 and 12

3

Find the GCF of 9, 12 and 18

4

Find the GCF of 8, 12 and 16

5

Find the GCF of 12, 15 and 20

6

Find the GCF of 18, 24 and 36

7

Find the GCF of 6, 9 and 12

8

Find the GCF of 15, 20 and 25

9

Find the GCF of 6, 10 and 12

10

Find the GCF of 12, 16 and 18

11

Find the GCF of 20, 25 and 30

12

Find the GCF of 12, 14 and 16

13

Find the GCF of 24, 36 and 40

14

Find the GCF of 10, 12 and 14

15

Find the GCF of 30, 45 and 60

16

Find the GCF of 4, 10 and 12

17

Find the GCF of 12, 16 and 20

18

Find the GCF of 18, 24 and 32

19

Find the GCF of 10, 12 and 15

20

Find the GCF of 8, 12 and 18

Answers Key

1

Find the GCF of 12, 15 and 18

3 is the GCF of 12, 15 and 18

Factors of 12

2 | 12 |

2 | 6 |

3 | 3 |

1 |

Factors of 15

3 | 15 |

5 | 5 |

1 |

Factors of 18

2 | 18 |

3 | 9 |

3 | 3 |

1 |

Factors of 12 = 2 x 2 x 3

Factors of 15 = 3 x 5

Factors of 18 = 2 x 3 x 3

Multiply all the common factors of 12, 15 and 18.

3 = 3

GCF(12, 15, 18) = 3

2

Find the GCF of 8, 10 and 12

2 is the GCF of 8, 10 and 12

Factors of 8

2 | 8 |

2 | 4 |

2 | 2 |

1 |

Factors of 10

2 | 10 |

5 | 5 |

1 |

Factors of 12

2 | 12 |

2 | 6 |

3 | 3 |

1 |

Factors of 8 = 2 x 2 x 2

Factors of 10 = 2 x 5

Factors of 12 = 2 x 2 x 3

Multiply all the common factors of 8, 10 and 12.

2 = 2

GCF(8, 10, 12) = 2

3

Find the GCF of 9, 12 and 18

3 is the GCF of 9, 12 and 18

Factors of 9

3 | 9 |

3 | 3 |

1 |

Factors of 12

2 | 12 |

2 | 6 |

3 | 3 |

1 |

Factors of 18

2 | 18 |

3 | 9 |

3 | 3 |

1 |

Factors of 9 = 3 x 3

Factors of 12 = 2 x 2 x 3

Factors of 18 = 2 x 3 x 3

Multiply all the common factors of 9, 12 and 18.

3 = 3

GCF(9, 12, 18) = 3

4

Find the GCF of 8, 12 and 16

4 is the GCF of 8, 12 and 16

Factors of 8

2 | 8 |

2 | 4 |

2 | 2 |

1 |

Factors of 12

2 | 12 |

2 | 6 |

3 | 3 |

1 |

Factors of 16

2 | 16 |

2 | 8 |

2 | 4 |

2 | 2 |

1 |

Factors of 8 = 2 x 2 x 2

Factors of 12 = 2 x 2 x 3

Factors of 16 = 2 x 2 x 2 x 2

Multiply all the common factors of 8, 12 and 16.

2 x 2 = 4

GCF(8, 12, 16) = 4

5

Find the GCF of 12, 15 and 20

1 is the GCF of 12, 15 and 20

Factors of 12

2 | 12 |

2 | 6 |

3 | 3 |

1 |

Factors of 15

3 | 15 |

5 | 5 |

1 |

Factors of 20

2 | 20 |

2 | 10 |

5 | 5 |

1 |

Factors of 12 = 2 x 2 x 3

Factors of 15 = 3 x 5

Factors of 20 = 2 x 2 x 5

Multiply all the common factors of 12, 15 and 20.

1 = 1

GCF(12, 15, 20) = 1

6

Find the GCF of 18, 24 and 36

6 is the GCF of 18, 24 and 36

Factors of 18

2 | 18 |

3 | 9 |

3 | 3 |

1 |

Factors of 24

2 | 24 |

2 | 12 |

2 | 6 |

3 | 3 |

1 |

Factors of 36

2 | 36 |

2 | 18 |

3 | 9 |

3 | 3 |

1 |

Factors of 18 = 2 x 3 x 3

Factors of 24 = 2 x 2 x 2 x 3

Factors of 36 = 2 x 2 x 3 x 3

Multiply all the common factors of 18, 24 and 36.

2 x 3 = 6

GCF(18, 24, 36) = 6

7

Find the GCF of 6, 9 and 12

3 is the GCF of 6, 9 and 12

Factors of 6

2 | 6 |

3 | 3 |

1 |

Factors of 9

3 | 9 |

3 | 3 |

1 |

Factors of 12

2 | 12 |

2 | 6 |

3 | 3 |

1 |

Factors of 6 = 2 x 3

Factors of 9 = 3 x 3

Factors of 12 = 2 x 2 x 3

Multiply all the common factors of 6, 9 and 12.

3 = 3

GCF(6, 9, 12) = 3

8

Find the GCF of 15, 20 and 25

5 is the GCF of 15, 20 and 25

Factors of 15

3 | 15 |

5 | 5 |

1 |

Factors of 20

2 | 20 |

2 | 10 |

5 | 5 |

1 |

Factors of 25

5 | 25 |

5 | 5 |

1 |

Factors of 15 = 3 x 5

Factors of 20 = 2 x 2 x 5

Factors of 25 = 5 x 5

Multiply all the common factors of 15, 20 and 25.

5 = 5

GCF(15, 20, 25) = 5

9

Find the GCF of 6, 10 and 12

2 is the GCF of 6, 10 and 12

Factors of 6

2 | 6 |

3 | 3 |

1 |

Factors of 10

2 | 10 |

5 | 5 |

1 |

Factors of 12

2 | 12 |

2 | 6 |

3 | 3 |

1 |

Factors of 6 = 2 x 3

Factors of 10 = 2 x 5

Factors of 12 = 2 x 2 x 3

Multiply all the common factors of 6, 10 and 12.

2 = 2

GCF(6, 10, 12) = 2

10

Find the GCF of 12, 16 and 18

2 is the GCF of 12, 16 and 18

Factors of 12

2 | 12 |

2 | 6 |

3 | 3 |

1 |

Factors of 16

2 | 16 |

2 | 8 |

2 | 4 |

2 | 2 |

1 |

Factors of 18

2 | 18 |

3 | 9 |

3 | 3 |

1 |

Factors of 12 = 2 x 2 x 3

Factors of 16 = 2 x 2 x 2 x 2

Factors of 18 = 2 x 3 x 3

Multiply all the common factors of 12, 16 and 18.

2 = 2

GCF(12, 16, 18) = 2

11

Find the GCF of 20, 25 and 30

5 is the GCF of 20, 25 and 30

Factors of 20

2 | 20 |

2 | 10 |

5 | 5 |

1 |

Factors of 25

5 | 25 |

5 | 5 |

1 |

Factors of 30

2 | 30 |

3 | 15 |

5 | 5 |

1 |

Factors of 20 = 2 x 2 x 5

Factors of 25 = 5 x 5

Factors of 30 = 2 x 3 x 5

Multiply all the common factors of 20, 25 and 30.

5 = 5

GCF(20, 25, 30) = 5

12

Find the GCF of 12, 14 and 16

2 is the GCF of 12, 14 and 16

Factors of 12

2 | 12 |

2 | 6 |

3 | 3 |

1 |

Factors of 14

2 | 14 |

7 | 7 |

1 |

Factors of 16

2 | 16 |

2 | 8 |

2 | 4 |

2 | 2 |

1 |

Factors of 12 = 2 x 2 x 3

Factors of 14 = 2 x 7

Factors of 16 = 2 x 2 x 2 x 2

Multiply all the common factors of 12, 14 and 16.

2 = 2

GCF(12, 14, 16) = 2

13

Find the GCF of 24, 36 and 40

4 is the GCF of 24, 36 and 40

Factors of 24

2 | 24 |

2 | 12 |

2 | 6 |

3 | 3 |

1 |

Factors of 36

2 | 36 |

2 | 18 |

3 | 9 |

3 | 3 |

1 |

Factors of 40

2 | 40 |

2 | 20 |

2 | 10 |

5 | 5 |

1 |

Factors of 24 = 2 x 2 x 2 x 3

Factors of 36 = 2 x 2 x 3 x 3

Factors of 40 = 2 x 2 x 2 x 5

Multiply all the common factors of 24, 36 and 40.

2 x 2 = 4

GCF(24, 36, 40) = 4

14

Find the GCF of 10, 12 and 14

2 is the GCF of 10, 12 and 14

Factors of 10

2 | 10 |

5 | 5 |

1 |

Factors of 12

2 | 12 |

2 | 6 |

3 | 3 |

1 |

Factors of 14

2 | 14 |

7 | 7 |

1 |

Factors of 10 = 2 x 5

Factors of 12 = 2 x 2 x 3

Factors of 14 = 2 x 7

Multiply all the common factors of 10, 12 and 14.

2 = 2

GCF(10, 12, 14) = 2

15

Find the GCF of 30, 45 and 60

15 is the GCF of 30, 45 and 60

Factors of 30

2 | 30 |

3 | 15 |

5 | 5 |

1 |

Factors of 45

3 | 45 |

3 | 15 |

5 | 5 |

1 |

Factors of 60

2 | 60 |

2 | 30 |

3 | 15 |

5 | 5 |

1 |

Factors of 30 = 2 x 3 x 5

Factors of 45 = 3 x 3 x 5

Factors of 60 = 2 x 2 x 3 x 5

Multiply all the common factors of 30, 45 and 60.

3 x 5 = 15

GCF(30, 45, 60) = 15

16

Find the GCF of 4, 10 and 12

2 is the GCF of 4, 10 and 12

Factors of 4

2 | 4 |

2 | 2 |

1 |

Factors of 10

2 | 10 |

5 | 5 |

1 |

Factors of 12

2 | 12 |

2 | 6 |

3 | 3 |

1 |

Factors of 4 = 2 x 2

Factors of 10 = 2 x 5

Factors of 12 = 2 x 2 x 3

Multiply all the common factors of 4, 10 and 12.

2 = 2

GCF(4, 10, 12) = 2

17

Find the GCF of 12, 16 and 20

4 is the GCF of 12, 16 and 20

Factors of 12

2 | 12 |

2 | 6 |

3 | 3 |

1 |

Factors of 16

2 | 16 |

2 | 8 |

2 | 4 |

2 | 2 |

1 |

Factors of 20

2 | 20 |

2 | 10 |

5 | 5 |

1 |

Factors of 12 = 2 x 2 x 3

Factors of 16 = 2 x 2 x 2 x 2

Factors of 20 = 2 x 2 x 5

Multiply all the common factors of 12, 16 and 20.

2 x 2 = 4

GCF(12, 16, 20) = 4

18

Find the GCF of 18, 24 and 32

2 is the GCF of 18, 24 and 32

Factors of 18

2 | 18 |

3 | 9 |

3 | 3 |

1 |

Factors of 24

2 | 24 |

2 | 12 |

2 | 6 |

3 | 3 |

1 |

Factors of 32

2 | 32 |

2 | 16 |

2 | 8 |

2 | 4 |

2 | 2 |

1 |

Factors of 18 = 2 x 3 x 3

Factors of 24 = 2 x 2 x 2 x 3

Factors of 32 = 2 x 2 x 2 x 2 x 2

Multiply all the common factors of 18, 24 and 32.

2 = 2

GCF(18, 24, 32) = 2

19

Find the GCF of 10, 12 and 15

1 is the GCF of 10, 12 and 15

Factors of 10

2 | 10 |

5 | 5 |

1 |

Factors of 12

2 | 12 |

2 | 6 |

3 | 3 |

1 |

Factors of 15

3 | 15 |

5 | 5 |

1 |

Factors of 10 = 2 x 5

Factors of 12 = 2 x 2 x 3

Factors of 15 = 3 x 5

Multiply all the common factors of 10, 12 and 15.

1 = 1

GCF(10, 12, 15) = 1

20

Find the GCF of 8, 12 and 18

2 is the GCF of 8, 12 and 18

Factors of 8

2 | 8 |

2 | 4 |

2 | 2 |

1 |

Factors of 12

2 | 12 |

2 | 6 |

3 | 3 |

1 |

Factors of 18

2 | 18 |

3 | 9 |

3 | 3 |

1 |

Factors of 8 = 2 x 2 x 2

Factors of 12 = 2 x 2 x 3

Factors of 18 = 2 x 3 x 3

Multiply all the common factors of 8, 12 and 18.

2 = 2

GCF(8, 12, 18) = 2