A fraction of a set

Primary 4 Fractions · Lesson video · 2 min 29 s

Primary 4 fraction of a set questions: divide a collection into equal groups, find the required part and connect the fraction to the number of objects.

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Questions in this lesson

  1. 0:06 Example 1: ['Mei has 30 cards. ', {'frac': ['2', '5']}, ' of them are blue and the rest are yellow.
  2. 1:07 Example 2: ['A bag has 32 beads. ', {'frac': ['3', '8']}, ' of them are red and the rest are blue.
Transcript

Mei has 30 cards. Two fifths of them are blue and the rest are yellow. How many blue cards does she have? Try it first. Pause if you like. Draw one bar for all 30 cards. Two fifths means 2 out of 5 equal units. So cut the bar into 5 equal units. 2 units are blue cards. The other 3 units are yellow cards. All 5 units make 30 cards. So 5 units is 30. 1 unit is 30 divided by 5, which is 6. The blue cards are 2 units. 2 times 6 is 12. So Mei has 12 blue cards.

A bag has 32 beads. Three eighths of them are red and the rest are blue. How many blue beads are there? Try it first. Pause if you like. Draw one bar for all 32 beads. Three eighths means 3 out of 8 equal units. So cut the bar into 8 equal units. 3 units are red beads. The rest are blue beads. The blue beads are 8 minus 3, which is 5 units. All 8 units make 32 beads. So 8 units is 32. 1 unit is 32 divided by 8, which is 4. The blue beads are 5 units. 5 times 4 is 20. So there are 20 blue beads. The denominator makes the equal units, and the numerator tells us how many units to take.