Grade 4 - Progress in Mathematics

Factor Trees

A composite number has more than two factors. 6 
 1  6


 2  3

A prime number is greater than 1 and has exactly

5 
 1  5

two factors, itself and 1.

The factors of a number that are prime are called

prime factors.

Yo u can use a factor tree to help you find all the

prime factors, or the prime factorization, of a number.

Look at these factor trees for 12.

12 12

3  4 6  2

3  2  2 3  2  2

3 and 2 are prime numbers.

So the prime factorization of 12 is 3  2 2.

Copy and complete each factor tree.

1. 30 2. 40 3. 54 4. 36

6  5 4  10 6  9 9 ?

? 2 ? ? 2 ?? 3 ??? ????

Draw a factor tree for each number.

5. 16 6. 10 7. 20 8. 24 9. 27


6. 32 11. 48 12. 35 13. 56 14. 72

6  2 
 12

3  2  2 
 12

3  4 
 12

3  2  2 
 12

4.2

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