Understand the idea.
Joining makes a new total
When objects join, keep the first group and add the arriving objects. The plus sign records this: . You can count everything, or keep eight in your head and count on only the four new objects.
Taking away leaves fewer
When objects are taken away, start with the whole collection and remove the named amount. Count only what stays. The minus sign records taking away: . Acting out the story helps you choose whether to add or subtract.
See the method in action.
More birds arrive
Eight birds are on a fence. Four more land. How many now?
Worked solution
- 1
Record the birds already there and those arriving.
All eight birds stay, and four more join them.
- 2
Count on four from eight.
Each new count includes one of the four arriving birds.
- 3
State the new total.
Twelve birds are now on the fence.
12 birds.
Blocks are put away
There are fifteen blocks. Put six away. How many stay out?
Worked solution
- 1
Start with all fifteen blocks.
Six blocks leave the group that stays out.
- 2
Take away five first.
Five of the six blocks are put away, leaving ten out.
- 3
Take away the last block.
Five and one make six, so nine blocks stay out.
9 blocks.
Try it yourself.
Check your understanding
Six children are playing. Three more join. Which calculation matches?
Show answer & reasoning
6 + 3 = 9
The six children stay and three children join them. Add the two groups: .
Keep practising
6 worksheet questions
Read the questions online
- Five shells and three more shells are joined. How many shells?
- Twelve pencils are out. Four are put away. How many remain?
- Nine children are on a bus. Two get off. How many stay?
- Seven red beads and six blue beads are joined. How many beads?
- There are eighteen counters. Take away eight. Write a calculation and answer.
- Ari has ten cards. Four cards are given to him. Is a matching calculation? Explain.
Read the worked solutions
- Five shells and three more shells are joined. How many shells?
.
8 shells. - Twelve pencils are out. Four are put away. How many remain?
.
8 pencils. - Nine children are on a bus. Two get off. How many stay?
Taking two away from nine leaves seven.
7 children. - Seven red beads and six blue beads are joined. How many beads?
.
13 beads. - There are eighteen counters. Take away eight. Write a calculation and answer.
Eighteen is ten and eight. Removing eight leaves ten.
. - Ari has ten cards. Four cards are given to him. Is a matching calculation? Explain.
He receives cards, so the total increases.
No. Use .
Curriculum reference & lesson scope
Australian Curriculum v9 and SA Curriculum Mathematics
Year 1 additive situations and number bonds within twenty.
Official curriculum source ↗