1
Subtraction stories
Discover Mathematics P2: Term 1, Lessons 11–20
GoalSolve take-away stories within 20 and write the number sentence.
New words
take away · to remove some and see what is leftleft · what remains after taking awaynumber sentence · numbers and signs that tell the story, like 9 − 4 = 5
Explanation
In a take-away story we start with some things and some go away. The question asks how many are left. Draw or imagine the things and cross out the ones that go. Then write a number sentence. Salma has 18 apples and gives 10 away. 18 − 10 = 8. Taking away a ten is easy: the ones stay the same. Another way is to think of adding: 15 − 6 is 6 + ? = 15.
Worked examples
Salma has 18 apples. She gives 10 to her neighbours. How many are left? 18 − 10 = 8.
Ahmed has 15 pears and gives 6 to his sister. 15 − 6 = 9. Check: 6 + 9 = 15.
Mina bought 13 oranges and gave 3 to her father. 13 − 3 = 10 oranges are left.
Class activity
Cross-out game. Put 12 small things, such as beans, on a plate. Take some away and ask: how many are left? Say the number sentence aloud, like 12 − 5 = 7. Take turns being the storyteller.
Practice
1
Karim had 14 pears. He ate 4. How many are left?
10 (14 − 4 = 10)
2
There are 17 birds on a wall. 9 fly away. How many birds are left?
8 (17 − 9 = 8)
3
Nour has 12 stickers. She gives 5 to Hana. How many does she have now?
7 (12 − 5 = 7)
4
Omar had 20 marbles and lost 10. How many marbles are left?
10 (20 − 10 = 10)
5
Write a number sentence: 19 flowers, 8 are picked.
19 − 8 = 11