Addition and subtraction within 20 – Year 1 maths worksheet answers to download as PDF

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1. Answer to Question 1

   1. 2 + 3 = 5. Check: 2 and 3 more is 3, 4, 5.
   2. 5 + 4 = 9. Start on 5, count on 4: 6, 7, 8, 9.
   3. 6 + 6 = 12. This is a double: 6 and 6.

2. Answer to Question 2

   1. Start on 7 and hop 5. 7 + 5 = 12.
   2. Start on 8 and hop 6. 8 + 6 = 14.
   3. Start on 9 and hop 3. 9 + 3 = 12.
   4. Start on 4 and hop 9. 4 + 9 = 13.
   5. Start on 6 and hop 7. 6 + 7 = 13.

3. Answer to Question 3

   1. The ten frame has 6 counters and 4 empty spaces. 6 + 4 = 10.
   2. 3 + 7 = 10.
   3. 2 + 8 = 10.
   4. 10 − 4 = 6.
   5. 10 − 9 = 1.

4. Answer to Question 4

   1. There are 7 counters. Cross out 2 of them and count the ones that are left: 1, 2, 3, 4, 5. The number sentence is 7 − 2 = 5.
   2. Start with 10 counters and cross out 4. Count back from 10: 9, 8, 7, 6. The number sentence is 10 − 4 = 6.
   3. There are 12 counters. Cross out 5 and count what is left: 7 counters. The number sentence is 12 − 5 = 7. Check with an addition: 7 + 5 = 12.

5. Answer to Question 5

   1. Start on 15 and count back 3. 15 − 3 = 12.
   2. Start on 18 and count back 5. 18 − 5 = 13.
   3. Start on 13 and count back 6. 13 − 6 = 7.
   4. Start on 20 and count back 8. 20 − 8 = 12.
   5. Start on 11 and count back 9. 11 − 9 = 2.

6. Answer to Question 6

   1. 9 + 3 = 12, 12 − 3 = 9, 12 − 9 = 3.
   2. 5 + 8 = 13, 13 − 5 = 8, 13 − 8 = 5.
   3. 7 + 8 = 15, 8 + 7 = 15, 15 − 8 = 7.

7. Answer to Question 7

   1. Add: 8 + 7. Bridge through 10: 8 + 2 = 10, then 10 + 5 = 15. 15 cakes.
   2. 8 + 7 = 15.
   3. 15 − 5 = 10 cakes.
   4. 10 + 4 = 14 cakes.

8. Answer to Question 8

   1. 9 + 6 = 15 marbles.
   2. 15 − 4 = 11 marbles.
   3. 11 + 3 = 14 marbles.
   4. 14 is less than 15, so fewer marbles. He has 1 fewer.

9. Answer to Question 9

   1. 12 − 5 = 7 ducks.
   2. 7 + 3 = 10 ducks.
   3. 12 − 5 = 7 and 7 + 3 = 10.
   4. Start 12, end 10. 12 is bigger, so there are fewer ducks at the end.

10. Answer to Question 10

    1. 11 + 8 = 19 books.
    2. 11 − 6 = 5 books.
    3. Blue 8 and red 5. 8 − 5 = 3 more on the blue shelf.
    4. 5 + 9 = 14 books.

11. Answer to Question 11

    1. Her friend gives her more, so we add: 13 + 5. Count on 5 from 13: 14, 15, 16, 17, 18. Priya has 18 stickers.
    2. Giving away means taking away: 18 − 7. Take 8 to reach 10, then put 1 back: 18 − 7 = 11 stickers.
    3. A new pack adds 4: 11 + 4 = 15 stickers.
    4. 15 is bigger than 13. To find how many more, count on from 13 to 15: 14, 15. That is 2 steps, so she ends with 2 more than she started with.

12. Answer to Question 12

    1. Add the red and the green carriages: 6 + 9. Start at 9 and count on 6: 10, 11, 12, 13, 14, 15. The train has 15 carriages.
    2. Zak takes 3 carriages off, so we subtract: 15 − 3 = 12 carriages left.
    3. Compare 12 and 10. 12 comes after 10 when we count, so 12 is bigger. Zak's train has more carriages now.
    4. Find the difference by counting on from 10 to 12: 11, 12. That is 2 steps, so Zak's train has 2 more carriages.

13. Answer to Question 13

    1. Fruit means the apples and the bananas: 7 + 4. Count on from 7: 8, 9, 10, 11. There are 11 pieces of fruit.
    2. They eat 6 of the 9 sandwiches: 9 − 6 = 3 sandwiches left.
    3. They eat 5 of the 7 apples: 7 − 5 = 2 apples left.
    4. Add what is left of both foods: 3 sandwiches + 2 apples = 5 things left. The bananas and the cake are not part of this question.

14. Answer to Question 14

    1. Add the two flavours sold at lunch: 9 + 8. Make 10 first: 9 + 1 = 10, then 10 + 7 = 17. So 17 ice creams are sold at lunchtime.
    2. Add the 6 sold in the afternoon: 17 + 6. Make 20 first: 17 + 3 = 20, then 20 + 3 = 23. 23 ice creams are sold altogether.
    3. The van started with 30. Take away the 23 sold: count on from 23 to 30, that is 7 steps. 7 ice creams are left. Check: 23 + 7 = 30.
    4. 23 is less than 25, because 23 comes before 25 when we count. So yes, she is right: they sold fewer than 25.

15. Answer to Question 15

    1. 14 − 6 = 8.
    2. 8 + 3 = 11.
    3. 11 − 5 = 6, then 6 + 8 = 14.
    4. Start 14, end 14. The bus is just as full: the same number.

16. Answer to Question 16

    1. 4 + 9 = 13, 5 + 8 = 13, 6 + 7 = 13. There are three pairs: (4, 9), (5, 8) and (6, 7).
    2. The smallest cards are 4 and 5. 4 + 5 = 9.
    3. The biggest are 8 and 9. 8 + 9 = 17.
    4. 4 + 6 = 10. Yes: the 4 and the 6.

17. Answer to Question 17

    1. 8 + 5 = 13, so wrong. He should write 13.
    2. 14 − 6 = 8, so right.
    3. 9 + 9 = 18, so right. It is a double.
    4. 15 − 7 = 8, so wrong. He should write 8.

18. Answer to Question 18

    1. 8 + 7 = 15 toys.
    2. 20 − 15 = 5 toys.
    3. 20 − 15 = 5. Check: 15 + 5 = 20. Correct.
    4. The third bag has 5 toys and the first bag has 8 toys. 5 is less than 8, so the third bag is less full.

19. Answer to Question 19

    1. 14 − 6 = 8. Check: 8 + 6 = 14.
    2. 13 − 5 = 8. Check: 13 − 8 = 5.
    3. C and C is a double. Half of 16 is 8. Check: 8 + 8 = 16.
    4. D and D make 12, so D is 6. Check: 12 − 6 = 6.

20. Answer to Question 20

    1. 3 + 6 = 9 and 4 + 5 = 9. The pairs are (3, 6) and (4, 5).
    2. The number 2 has no partner. 2 needs 7.
    3. 3 + 6 = 9, so the other number is 6.
    4. 5 + 6 = 11 is the only pair. (5, 6).