1. What is the biggest number that you
can divide both 16 and 24 by?
2. Learning Target:
Students will learn how to find the
greatest common factor (GCF) of two
or more numbers and they will learn
the different strategies for doing so.
3. A common factor is a whole number
that is a factor of two or more nonzero
whole numbers.
The biggest of the common factors is
called the greatest common factor
(GCF)
4. There are 3 methods for finding the GCF.
1. List all the factors. (rainbow)
2. Factor Tree and multiply the common
numbers to find GCF.
3. CAKE – multiply the numbers on the left
side of the cake
5. Find the GCF of 14, 35.
1. List all the factors. (rainbow)
14: 1, 2, 7, 14
35: 1, 5, 7, 35
Common factors: 1, 7
GCF: 7
6. Find the GCF of 12, 54
2. Factor Tree and multiply the
common numbers to find GCF.
12 54
3 4 6 9
3 2 2 2 3 3 3
2 x 3 = 6 GCF = 6
7. Find the GCF of 27, 45
3. CAKE – multiply the numbers on the left
side of the cake
2, 3, 5, 7, 11, 13
3 27 45
3 9 15
3 5
GCF = 3 x 3 = 9
8. CAKE works the same as the ladder
except both numbers must be divisible
by the number before you write it
down in each step and you stop when
one or both of your numbers turn
prime. Then to find the GCF you
multiply the numbers on the left side
of the cake. This works the same when
you are given three numbers.
9. Find the GCF using any of the methods.
20, 75
12, 21, 30
