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Lesson · Grade 6 · Mathematics

Prime factorization with a factor tree

  • Grade 6
  • Mathematics
  • 1 min 18 s
  • British Columbia
  • BC6-MA-09

A factor tree splits 300 into 3 × 100, then 100 into 10 × 10, then each 10 into 2 × 5, circling every prime where a branch stops. The circled primes are written smallest first as 300 = 2 × 2 × 3 × 5 × 5 and multiplied back together (4, 12, 60, 300) to check the answer.

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In one sentence

The question this lesson answers

How can we write 300 as a product of prime numbers?

A prime number has exactly two factors, 1 and itself, like 2, 3, 5 and 7.

Transcript

What the lesson says

How can we write 300 as a product of prime numbers?

A prime number has exactly two factors, 1 and itself, like 2, 3, 5 and 7.

Start the tree by splitting 300 into two factors: 3 times 100.

3 is prime, so circle it.

100 is not prime, so split it into 10 times 10.

Each 10 splits into 2 times 5.

2 and 5 are both prime, so circle them too.

Now every branch ends in a prime, so the tree is finished.

Write the circled primes in a row, from smallest to largest.

This is the prime factorization of 300: 2 times 2 times 3 times 5 times 5.

Check it by multiplying them back together.

2 times 2 is 4, and 4 times 3 is 12.

12 times 5 is 60, and 60 times 5 is 300.

A factor tree splits a number until every branch ends in a prime.

Curriculum

Where this fits

British Columbia, Grade 6

Mathematics, Number: factors and multiples: greatest common factor and least common multipleBC6-MA-09

Previous: Divisibility Rules for 2, 3, 4, 5, 6, 9 and 10Next: Greatest Common Factor with a Venn Diagram

The outcomes and strands follow the British Columbia curriculum.

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