Year 9 maths lesson · Fractions

Expressing a Quantity as a Fraction

Express one quantity as a fraction of another and simplify the result. Covers both direct problems (the part is given) and indirect problems (you need to calculate the part first).

  • About 3–5 minutes
  • 5 quick questions as you go
  • Then about 5 minutes of practice
Practice questions → Set for Class

Worked examples

What fraction of 125 students are girls (65)?

  1. Part = 65, total = 125 → 65/125
  2. Both divide by 5: 65 ÷ 5 = 13, 125 ÷ 5 = 25
  3. 65/125 = 13/25

30 lollies, 12 red, rest blue — what fraction are blue?

  1. Calculate the part first: 30 − 12 = 18 blue
  2. Write the fraction: 18/30
  3. Simplify: 18 ÷ 6 = 3, 30 ÷ 6 = 5
  4. 18/30 = 3/5

Before this lesson

It helps to be comfortable with:

Lesson transcript

Everything the lesson says, word for word

Let’s say a school has 125 students and 65 are girls. What fraction of the students are girls? There are 125 students in total, so that’s what it’s out of. We have 65 girls out of 125 total students. So we can write this as 65 over 125. Now we simplify. Both 65 and 125 divide by 5. 65 divided by 5 is 13, and 125 divided by 5 is 25. So the fraction is 13 over 25.

Now here’s one where we need to figure out the part first. A bag has 30 lollies. 12 are red and the rest are blue. What fraction are blue? First, work out how many are blue. 30 minus 12 equals 18. So it’s 18 blue out of 30 total. Write that as 18 over 30. Next we simplify our fraction. So the answer is 3 over 5.

More Fractions lessons

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