Subtraction by counting back
Answers are for parents and teachers.
1
Put 15 spoons on the table. Take away 6, one at a time, counting back from 15. How many are left?
9 spoons (15 − 6).
2
Show 14 − 5 on a number line in two ways: five small jumps and one big jump.
Both ways land on 9.
3
Ask a grown-up to pick two numbers up to 20, such as 4 and 10. Find the difference between them.
Any correct difference, such as 6 for 4 and 10.
4
Show 17 − 8 by going back to 10 first. How many do you jump back first? How many more?
7 back to 10, then 1 more. The answer is 9.
5
What happens when you take away 0? Give two examples.
The number stays the same, such as 12 − 0 = 12 and 5 − 0 = 5.