3
Hop back to take away
Joyful Mathematics: Chapter 5
GoalTake away by hopping backwards on a number line.
New words
back · the other way, towards 0hop back · jump to a smaller numbercount back · say the numbers going down
Explanation
To take away, hop backwards. Look at 10 − 4. Start at 10. Hop back 4 steps: 9, 8, 7, 6. You land on 6. So 10 − 4 = 6. When we take away, the number gets smaller.
Worked examples
7 − 2 = 5. Start at 7. Hop back 2 steps.
8 − 5 = 3. Start at 8. Hop back 5 steps.
6 − 3 = 3. Hop back 1, 1 and 1.
Class activity
Count-back game. The grown-up says a start number and the steps back, for example "Start at 9 and go back 2." The child claps while counting back: 8, 7. Then the child says where they landed. Play with five different sums.
Practice
1
Start at 8. Hop back 3 steps. Where do you land?
5.
2
Start at 6. Hop back 4 steps. Where do you land?
2.
3
Start at 9. Hop back 2 steps. Where do you land?
7.
4
What is 10 − 1?
9.
5
Start at 7. Hop back 5 steps. Where do you land?
2.