2
Writing a weight story
Discover Mathematics P2: Term 1, Lessons 51–60
GoalWrite my own story problem about mass from a number sentence, and check that the question matches.
New words
story problem · a short story that ends with a math questionquestion · the part of the story we need to answercheck · see that the answer makes sense
Explanation
You can write a story problem yourself. Start with a number sentence, such as 9 kg + 6 kg = 15 kg. Think of a who and a what: Marina carries 9 kg of oranges and 6 kg of guavas. Then ask a question: how many kilograms of fruit does she carry in all? The question must fit the sign. ‘In all’ goes with adding. ‘How many are left’ goes with taking away. Finally solve your problem and check the answer.
| Step | Example |
|---|---|
| 1. Number sentence | 9 kg + 6 kg = 15 kg |
| 2. Who and what | Marina, oranges and guavas |
| 3. Question | How many kg in all? |
Worked examples
From 9 kg + 6 kg: Marina carries 9 kg of oranges and 6 kg of guavas. How many kg of fruit does she carry in all? Answer: 15 kg.
From 80 g − 30 g: Nour has 80 g of nuts. She gives 30 g to her brother. How many grams does she have left? Answer: 50 g.
A wrong question: ‘Nour has 80 g of nuts and gives away 30 g. How many grams in all?’ The story takes away, so ask ‘how many are left?’.
Class activity
Story swap. Each person writes one weight story on a small card with a number sentence on the back. Swap cards. Solve the other person’s story, write the number sentence with the unit, and check it against the card. Use kg for heavy things and g for light things.
Practice
1
Write a story for 12 kg + 9 kg. What is the answer?
Any fitting story. The answer is 21 kg.
2
Tarek has 15 kg of dates and sells 4 kg. ‘How many kg in all?’ What is wrong with this question? Write a better one and solve it.
It takes away, so ask ‘How many kg are left?’ 15 − 4 = 11 kg.
3
Write a take-away story for 50 g − 20 g.
Any fitting story. The answer is 30 g.
4
Which number sentence fits: Omar has 7 kg of nuts and buys 5 kg more?
7 + 5 = 12 kg.
5
A bag of flour is 16 kg and a bag of sugar is 9 kg. How many kg more is the flour?
16 − 9 = 7 kg more.