Addition in any order
Understand and apply the commutative property of addition: addends can be added in any order
What a learner can do afterwards
- Explain that 3 + 8 gives the same answer as 8 + 3
- Use commutativity to choose the larger number to count on from
- Demonstrate that subtraction is not commutative (5 − 3 ≠ 3 − 5)
1 · Read
You already know how to put two groups together to add. Here is a neat trick: it does not matter which number you say first. 3 + 8 and 8 + 3 both give the same answer, 11.
Mia picks 4 red apples and 5 green apples. She counts the red ones first: 4 + 5 = 9 apples. Next time she counts the green ones first: 5 + 4 = 9 apples. Same total, either way.
When you count on, start from the bigger number. It is faster. For 3 + 8, start at 8 and count on: 9, 10, 11.
Addition can flip, but subtraction cannot. 5 - 3 is not the same as 3 - 5. Order only stays free for addition.
Add numbers in any order and the answer stays the same, but subtraction always keeps its order.
2 · Watch
Take it off screen
Where it sits
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
14 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.