Week 26 · Fact families, mass and perimeter · 3 lessons
2
Division stories and mass of fruit
Discover Mathematics P3: Term 2, Lessons 101–110
GoalWrite division stories and find the mass of groups of fruit in grams.
New words
mass · how heavy something isgram (g) · a small unit of mass; 1,000 g = 1 kgstory · a short problem told in words
Explanation
A division equation can be told as two kinds of story. Take 32 ÷ 8 = 4. Sharing story: 32 rolls are shared equally into 8 bags, so each bag has 4 rolls. Grouping story: 32 rolls are packed with 8 in each bag, so there are 4 bags. To write your own story, choose a place, such as a bakery or a school, say what the total is and what happens to it. Mass problems use multiplication and division too. If one apple has a mass of 150 g, then 4 apples have a mass of 4 × 150 = 600 g. If one orange has a mass of 200 g, then 4 oranges have 4 × 200 = 800 g. To find how much more the oranges weigh, subtract: 800 − 600 = 200 g.
Worked examples
Kind
Story
Answer
Sharing
32 rolls into 8 bags
4 in each bag
Grouping
32 rolls, 8 in each bag
4 bags
Two stories for 32 ÷ 8 = 4. In the sharing story each bag gets 4 rolls. In the grouping story there are 4 bags.
Each apple has a mass of 150 g. Four apples have a mass of 4 × 150 = 600 g.
Four oranges have a mass of 4 × 200 = 800 g. Four apples have 600 g. The scale tips toward the oranges, which are 800 − 600 = 200 g heavier. Together the fruit has a mass of 600 + 800 = 1,400 g, which is 1 kg 400 g.
Class activity
Story book. Choose three division equations such as 18 ÷ 3 = 6, 40 ÷ 5 = 8 and 36 ÷ 4 = 9. For each, write one sharing story and one grouping story with your own people and places. Swap with a partner, who must write the equation for each story. If you have a kitchen scale, weigh 4 pieces of the same fruit together and say what one piece weighs about.
Practice
1
Write a sharing story for 24 ÷ 6 = 4.
Answers vary, for example: Mina shares 24 dates equally among 6 plates, so there are 4 dates on each plate.
2
Write a grouping story for 30 ÷ 5 = 6.
Answers vary, for example: A baker packs 30 rolls with 5 rolls in each bag, so he fills 6 bags.
3
One pear has a mass of 120 g. What is the mass of 5 pears?
5 × 120 = 600 g.
4
The 4 oranges together have a mass of 800 g. All the oranges are the same. What is the mass of one orange?
800 ÷ 4 = 200 g.
5
Youssef buys 4 apples of 150 g each and 4 oranges of 200 g each. What is the total mass in grams? Write it in kg and g too.
4 × 150 = 600 g and 4 × 200 = 800 g. Total: 600 + 800 = 1,400 g, which is 1 kg 400 g.
