NumbersExercise 38 - Example (Page 1) HomeHWFORKIDS Numbers Exercises Page1 of 2 Page2 of 2

2. Find the GCF of 180, 72, and 210. (Method 2):

 Find the factors:(Start with 2,3,4...) 2|180 2|90 3|45 3|15    5 2|72 2|36 2|18 3|9    3 2|210 3|105 5|35    7
Factors of 180 = 2 x 2 x 3 x 3 x 5

Factors of 72 = 2 x 2 x 2 x 3 x 3

Factors of 210 = 2 x 3 x 5 x 7

Common factors of 180, 72 and 210 are: 2 and 3

GCF = 2 x 3 = 6

3. Find the GCF of 14, 28, and 42. (Method 2):

 Find the factors:(Start with 2,3,4...) 2|14    7 2|28 2|14    7 2|42 3|21    7
Factors of 14 = 2 x 7

Factors of 28 = 2 x 2 x 7

Factors of 42 = 2 x 3 x 7

Common factors of 14, 28 and 42 are: 2 and 7

GCF = 2 x 7 = 14

4. Find the LCM of 180, 72, and 210. Factorization Method:

 Find the factors:(Start with 2,3,4...) 2|180 2|90 3|45 3|15    5 2|72 2|36 2|18 3|9    3 2|210 3|105 5|35    7
Factors of 180 = 2 x 2 x 3 x 3 x 5 = 22 x 32 x 5

Factors of 72 = 2 x 2 x 2 x 3 x 3 = 23 x 32

Factors of 210 = 2 x 3 x 5 x 7

Take all the highest factors = 23 x 32 x 5 x 7 = 2520

5. Find the LCM of 180, 72, and 210. Division Method:

 2|210, 180, 72 2|105, 90, 36 2|105, 45, 18 3|105, 45, 9 3|35, 15, 3 5|35, 5, 1   7, 1, 1 L.C.M = 2 x 2 x 2 x 3 x 3 x 5 x 7 = 2520

6. G.C.F. of 12 and 20 = 4
L.C.M. of 12 and 20 = 60
Product of above G.C.F and L.C.M = 4 x 60 = 240
Product of 12 and 20 = 240
G.C.F x L.C.M of two numbers = Product of the numbers
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