P3 Mathematics: Addition and Subtraction Word Problems
Primary 3 · Mathematics · Term 1 · Addition and Subtraction Word Problems · 60 min
Syllabus objectives
- Construct number sentences and number stories
Specific Objectives
By the end of the lesson, pupils should be able to: 1. Translate addition and subtraction word stories into number sentences using '+', '-' and '=' signs. 2. Create original addition and subtraction stories based on a given number sentence.
Mathematical Language
- Number story: A short story that uses numbers and requires a calculation to find an answer. - Number sentence: A way of writing a math problem using numbers and symbols (e.g., 5 + 2 = 7). - Altogether: A word often used in addition stories meaning to join groups. - Left: A word often used in subtraction stories meaning what remains after some are taken away.
Resources
- Whiteboard and markers - Large picture cards showing local scenes (market, beach) - Counters (bottle tops) - Small individual whiteboards and pens
Mental Test
1. What is 10 more than 45? (55) 2. Double 6. (12) 3. What is 20 minus 5? (15) 4. How many tens are in 80? (8) 5. Start at 12 and count on 4. What number are you at? (16) 6. What is the sum of 7 and 3? (10) 7. If I have 5 mangoes and buy 5 more, how many do I have? (10) 8. What number comes just before 100? (99)
Lesson Review
- Teacher: Writes '12 + 5 = 17' on the board. 'What do we call the symbols between the numbers?' - Pupils: Identify the plus sign and the equals sign. - Teacher: 'If I have 10 and I take away 3, what is the answer?' - Pupils: 7. - Teacher: 'Show me on your fingers how we represent "taking away"'. - Pupils: Fold fingers down to show subtraction.
Motivation
- Teacher: Shows a picture of a bus at the Victoria Terminal. 'Imagine there are 8 people on this bus. At the first stop in Plaisance, 3 people get off. How can we tell this as a math story?' - Pupils: Share their ideas about what happened to the number of people. - Teacher: 'Today we are going to learn how to turn these stories into number sentences and how to make our own stories from numbers.'
Conceptual Development
- Teacher: Displays a picture of 5 coconuts. 'I found 5 coconuts. My brother found 4 more. How many do we have altogether?' - Teacher: 'Let's turn this into a number sentence. The first number is 5. We added more, so we use the plus (+) sign. The next number is 4. The equals (=) sign tells us the total.' Writes '5 + 4 = 9' on the board. - Pupils: Use bottle tops to model the story (5 tops, then add 4 tops, count 9). - Teacher: 'Now let's try a subtraction story. There were 10 fish in a net. 4 swam away. How many are left?' - Teacher: 'We start with 10. Swam away means minus (-). We take away 4. 10 - 4 = 6.' - Pupils: Write '10 - 4 = 6' on their individual whiteboards. - Practice 1: Teacher gives a story: 'Maria had 15 Rupees. She spent 5 Rupees on a banana. How much is left?' - Pupils: Write the number sentence (15 - 5 = 10). - Teacher: 'Now let's go backwards. I give you a number sentence: 7 + 3 = 10. Who can make a story about birds?'. - Pupils: 'There were 7 birds on a tree. 3 more flew there. Now there are 10 birds.' - Practice 2: Teacher writes '12 - 2 = 10'. - Pupils: Work in pairs to tell a story about 12 shells at the beach.
Individual Activity
Assessment Criteria: Teacher looks for correct selection of operations (+ or -) and correct placement of numbers in the sentence. (a) Support Group: Provide a worksheet with pictures. Task 1: Look at a picture of 6 apples and 2 more being added. Fill in the boxes: [ ] + [ ] = [ ]. Task 2: A story is read: 'Tom has 5 cars. He loses 1.' Circle the correct sentence: 5 + 1 = 6 OR 5 - 1 = 4. Answers: 6 + 2 = 8; 5 - 1 = 4. (b) Expected Level Group: Task 1: Write number sentences for these stories: i. 12 birds were in a tree. 5 flew away. (12 - 5 = 7) ii. I have 8 red pens and 6 blue pens. How many pens in total? (8 + 6 = 14) Task 2: Look at the sentence 9 + 4 = 13. Write a short story about cakes. Answers: Stories will vary but must involve 9 and 4 being combined to make 13. (c) Challenge Group: Task 1: Write a number sentence for this story: 'There were 20 eggs. 5 were broken and 2 were eaten. How many are left?' (20 - 5 - 2 = 13 or 20 - 7 = 13). Task 2: Create two different stories for the number sentence 15 - 8 = 7. One story must use the word 'left' and one story must use the word 'gave away'.
Conclusion
- Teacher: 'What sign do we use when things are added together?' - Pupils: The plus sign (+). - Teacher: 'What sign do we use when things are taken away or lost?' - Pupils: The minus sign (-). - Teacher: 'If I say "I have 10 sweets and I give 2 to my friend", is that 10 + 2 or 10 - 2?' - Pupils: 10 - 2. - Teacher: Recaps that number sentences are just a short way to write our math stories.
Project Work
Math Story Collector: Go home and find two groups of items (e.g., 5 spoons and 3 forks). Draw the items, write a 'number story' about them, and then write the matching number sentence to show the total.