Question 1
Work out: 9 + 4 = __
Year 1
Add and subtract one-digit and two-digit numbers to 20, including zero
Use counters and number sentences to add to 20, subtract from 20, and notice what happens when we add or subtract zero.
Lesson overview
Number - addition and subtraction
Addition means putting groups together. Subtraction means taking some away from the whole group. Zero means none, so adding zero keeps the number the same and subtracting zero also keeps the number the same.
Worked example
Work out 12 - 4.
- Start with 12 counters.
- Take away 4 counters.
- Count the counters left behind.
- There are 8 counters left, so 12 - 4 = 8.
Try it
Use the counters and number sentences to work out each answer.
Question 2
Work out: 15 - 3 = __
Question 3
Which number sentence matches the counters?
Question 4
Work out: 18 - 8 = __
Question 5
Which sign makes this true: 7 __ 5 = 12?
Common mistakes
These reminders help when adding, subtracting and using zero.
- Counting all the counters again after subtracting instead of counting what is left.
- Mixing up the two signs and adding when the question says subtract.
- Thinking that adding zero changes the number.
Related topics
These connect closely to adding and subtracting within 20.
- Represent and use number bonds and related subtraction facts within 20.
- Solve one-step problems that involve addition and subtraction, using objects and pictures.