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Lesson · Grade 7 · Mathematics

Equivalent fractions and lowest form

  • Grade 7
  • Mathematics
  • 1 min 9 s
  • British Columbia
  • BC7-MA-30

Fraction bars show that 8/12, 4/6 and 2/3 shade the same amount, because dividing (or multiplying) the top and bottom by the same number makes an equivalent fraction. The video then checks that only 1 divides both 2 and 3, and shows that dividing by the GCF, 4, gets 8/12 to its lowest form, 2/3, in one step.

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In one sentence

The question this lesson answers

How do we write eight twelfths in lowest form?

Here is a bar cut into 12 equal parts, with 8 of them shaded.

Transcript

What the lesson says

How do we write eight twelfths in lowest form?

Here is a bar cut into 12 equal parts, with 8 of them shaded.

Grouping the parts in twos makes 6 equal parts, with 4 shaded.

Grouping them in twos again makes 3 equal parts, with 2 shaded.

The shaded amount never changed, so all three fractions are equivalent.

Each time, we divided the top and the bottom by the same number, 2.

Multiplying the top and the bottom by the same number works too.

Only 1 divides both 2 and 3, so we cannot divide any further.

That means eight twelfths in lowest form is two thirds.

A faster way uses 4, the greatest common factor, or GCF, of 8 and 12.

Dividing the top and the bottom by 4 gets to two thirds in one step.

To write a fraction in lowest form, divide the top and the bottom by their greatest common factor.

Curriculum

Where this fits

British Columbia, Grade 7

Mathematics, Number: relationships between decimals, fractions, ratios, and percentsBC7-MA-30

Previous: Why 1/3 is 0.333...Next: Comparing fractions on a number line

The outcomes and strands follow the British Columbia curriculum.

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