GCF-LCM In-class Exercise - page 1

Name ______________

Find the greatest common factor (GCF) of these pairs of numbers:
1. Write out the factors of both numbers to their right.
2. Find the biggest one that appears in both lists and circle it.

1). (I'll start you out:)
Factors of 35: 1, 5, 7
Factors of 25: ________________
    GCF = _____		 2).
Factors of 14: ________________
Factors of 28: _________________
    GCF = _____		 3).
Factors of 40: ________________
Factors of 18: ________________
    GCF = _____
4).
Factors of 14: ________________
Factors of 42: ________________
    GCF = _____		 5).
Factors of 18: ________________
Factors of 33: ________________
    GCF = _____		 6).
Factors of 24: ________________
Factors of 16: ________________
    GCF = _____

Find the least common multiple (LCM) of these pairs of numbers by using the LCM formula:

LCM(a,b) = (a x b) / GCF(a,b)
The pairs of numbers below are the same as above, so you can use the GCFs you found to find their LCM:

7).
LCM (35,25) = (35 x 25) / _____ = _____
 8).
LCM (14,28) = ______________ = _____
9).
LCM (40,18) = _______________ = ____

 10).
LCM (14,42) = _______________ = ____
11).
LCM (18,33) = _______________ = ____		 12).
LCM (24,16) = _______________ = ____