GMy GYM MathMOE-aligned Primary Maths
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P5 · Topic

Fractions

Use a common denominator, then work in units of the whole.

Big Idea
Use a common denominator, then work in units of the whole.
1/41/4 as a bar
Circle and bar show the same fraction.
Key points
  1. 1Convert mixed numbers to improper fractions before × or ÷.
  2. 2For + and −, find a common denominator first.
  3. 3'Of' means multiply. 'Remainder' means what is left over.
  4. 4Draw a bar to see the units clearly.
Worked example
  1. 1Change is 5/6 − 2/3 = 5/6 − 4/6 = 1/6 of the tank.
  2. 21/6 of tank = 15 L.
  3. 3Full tank = 6 × 15 = 90 L.
Answer: 90 L
GYM Teaching Tip
Always ask: fraction of what? Redraw the bar after each step.
See the question behind this example
A tank is 2/3 full. After adding 15 L it is 5/6 full. Find the capacity of the tank.