New
New
Year 2

Add three addends efficiently

I can add three addends efficiently.

New
New
Year 2

Add three addends efficiently

I can add three addends efficiently.

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Lesson details

Key learning points

  1. The order of the addends can be changed to make the addition easier
  2. The sum will be the same whichever pair of addends we add first.
  3. Finding a known fact or double to add first can be more efficient.
  4. Strategies used to be efficient might be different for everyone.

Keywords

  • Addends - Any of the numbers that are added together.

  • Efficient - Not wasting time or effort. An efficient strategy is one we can carry out easily.

  • Strategy - A plan or method to achieve a specific goal.

Common misconception

Children unable to understand that addends can be swapped but the sum will remain the same.

Use a number line to explore commutativity in a situation where it looks less obvious as this will show children the different structures but also different starting pints but the end pint will remain the same.

It is much more obvious that we can change the order of the addends in the context of aggregation. For example, children can see much more easily that: 3 + 1 + 4 = 1 + 3 + . In the second LC, we encourage independence, asking the children to note which addends to add together first.
Teacher tip

Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

Lesson video

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6 Questions

Q1.
What is the sum of the three addends?
An image in a quiz
Correct Answer: 9
Q2.
Look at each expression and match to the correct description.
Correct Answer:3 + 2 + 4,less than 10

less than 10

Correct Answer:6 + 1 + 3,equal to 10

equal to 10

Correct Answer:3 + 2 + 6,greater than 10

greater than 10

Q3.
What will the third addend be to make the expression sum to 10?
Correct Answer:1 + 2,+ 7

+ 7

Correct Answer:2 + 3 ,+ 5

+ 5

Correct Answer:3 + 4,+ 3

+ 3

Correct Answer:4 + 5,+ 1

+ 1

Q4.
Match the double fact to the correct answer.
Correct Answer:Double 6 is,12

12

Correct Answer:Double 4 is,8

8

Correct Answer:Double 3 is,6

6

Correct Answer:Double 5 is ,10

10

Q5.
Which equations represent the part-part-whole model?
An image in a quiz
Correct answer: 2 + 1 + 7 = 10
1 = 10 + 7 + 2
2 + 10 + 1 = 7
Correct answer: 10 = 1 + 2 + 7
Q6.
Laura has been adding three addends by combining different pairs. Match each starting expression to her new equation.
Correct Answer:1 + 4 + 3,5 + 3 = 8

5 + 3 = 8

Correct Answer:2 + 6 + 1,8 + 1 = 9

8 + 1 = 9

Correct Answer:5 + 4 + 1,5 + 5 = 10

5 + 5 = 10

Correct Answer:3 + 1 + 7 ,4 + 7 = 11

4 + 7 = 11

6 Questions

Q1.
True or false. The order of the addends can be changed to make the addition easier.
Correct answer: True
False
Q2.
The image shows Aisha's strategy for adding three addends. What strategy did she use?
An image in a quiz
Correct answer: 2 + 3 = 5 then add 5
2 + 5 = 7 then add 3
3 + 5 = 8 then add 2
Q3.
Lucas used this strategy to add the three addends. Order the steps taken in his strategy
An image in a quiz
1 - I found double 4
2 - Double 4 is 8
3 - I added 8 and 2
4 - The sum is 10
Q4.
Which step has been taken in solving this equation?
An image in a quiz
Correct answer: Using a known double fact.
Finding the total of the first two addends.
Finding the total of the last two addends.
Q5.
Match the expression to the equation that could be used to calculate the sum.
Correct Answer:1 + 8 + 1,8 + 2 = 10

8 + 2 = 10

Correct Answer:1 + 5 + 4,5 + 5 = 10

5 + 5 = 10

Correct Answer:6 + 3 + 1,6 + 4 = 10

6 + 4 = 10

Q6.
Solve the equations using an efficient strategy.
Correct Answer:2 + 4 + 2 =,8

8

Correct Answer:5 + 1 + 4 =,10

10

Correct Answer:1 + 5 + 5 =,11

11

Correct Answer:5 + 2 + 2 =,9

9

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