GMy GYM MathMOE-aligned Primary Maths
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P6 · Topic

Ratio

Use units on a bar model. Keep total units clear.

Big Idea
Use units on a bar model. Keep total units clear.
BoysGirls2 : 3part : part
Compare one group with another. Order matters.
Key points
  1. 1Simplify ratios by dividing by the HCF.
  2. 2Change-of-quantity: check if total, difference or one part is constant.
  3. 3Convert between ratio and fraction: 2 : 3 → 2/5 and 3/5.
  4. 4Same units for both sides (all in $, all in kg).
Part to whole
2 of 5whole = 5 unitsBoys : Total = 2 : 5

Add the parts to see the whole.

Total units
Total 40 shared in 2 : 3888885 units = 401 unit = 40 ÷ 5 = 8

Total ÷ total units = 1 unit.

Worked example
  1. 13 units = 24, so 1 unit = 8.
  2. 2Blue = 5 units = 5 × 8 = 40.
Answer: 40
GYM Teaching Tip
Draw the bar model before you compute.
See the question behind this example
The ratio of red to blue marbles is 3 : 5. There are 24 red marbles. How many blue marbles?