Greatest Common Factors a.k.a. GCF

Greatest Common Factors When two numbers share a factor, that factor is called a common factor. Factors of 8: 1, 2, 4, 8 Factors of 12: 1, 2, 3, 4, 6, 12 The common factors of 8 and 12 are 1, 2, and 4. The greatest common factor is the largest factor shared by two or more numbers. The greatest common factor of 8 and 12 is 4.

Examples Find the common factors and greatest common factor of 10, 20, and 30. First list the factors of each number. factors of 10: ________________________ factors of 20: ________________________ factors of 30: ________________________ Then list all of the common factors: ___________ Finally, compare these factors to find the greatest common factor: __________

TOTD 1/8/15 List all the factors of each number and then identify the number as prime or composite. 35:_______________ P or C 51: _______________ P or C List the factors of each number. Then find the greatest common factor of the numbers. 3) 12, 14: ___________________GCF ____________ 4) 6, 21: ____________________GCF ____________ Multiply. 5) 8.91 x 3.2 Divide. 6) 31.05 ÷ .9