Part of MathsAdding and subtractingYear 3
Watch this Teacher Talk and discover how to add three 1-digit numbers together using number bonds.
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Here is a calculation with three numbers being added:
5 + 4 + 1 = 10
If the numbers are written in a different order, what happens to the answer?
4 + 5 + 1 = 10
What about another order?
1 + 4 + 5 = 10
We say that addition is commutative because whichever order we add the three numbers, the answer is the same.
Let's try another calculation.
6 + 2 + 1 = 9
Now let's change the order.
6 + 1 + 2
What about this?
1 + 2 + 6?
The total is 9 for all these sums, the numbers have just been added in a different order.
Joe walks 3 km from home to school, then 4 km from school to Sophie's house, then 2 km from Sophie's house back home.
(i) How far does he walk altogether doing that journey?
(ii) If Joe walked from home to Sophie's house then to school and then back home, how far does he walk?
鉁 Joe walks 3 km + 4 km + 2 km = 9 km altogether.
鉁 If Joe walked from home to Sophie's house then to school and then back home Joe walks 2 km + 4 km + 3 km = 9 km
8 + 4 + 3 = 15
Can you find three other ways to add these numbers to make 15?
Here are a few you could choose:
鉁 4 + 3 + 8 = 15
鉁 8 + 3 + 4 = 15
鉁 3 + 4 + 8 = 15
鉁 4 + 8 + 3 = 15
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Find out more by working through a topic
Addition and subtraction methods
Adding decimals with the same number of decimal places (formal method)
Subtract more than 4-digit numbers
Adding decimals with a different number of decimal places