New
New
Year 3

# Use known facts to find complements to 100 efficiently

I can use known facts to find complements to 100 efficiently.

New
New
Year 3

# Use known facts to find complements to 100 efficiently

I can use known facts to find complements to 100 efficiently.

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## Lesson details

### Key learning points

1. Number facts to 10 can be applied to multiples of 10
2. Using pairs to 10 and pairs to 100 we can find pairs to 100
3. If we have a pair to 10 then the tens have to total 90 for the whole to be 100
4. A number line can represent the complements to 100

### Common misconception

Pupils may be less efficient if they are not fluent with bonds within 10 e.g. 3 + 6 = 9

Provide additional scaffolding as appropriate including examples of pairs that total 9 and 10

### Keywords

• Complement to 100 - Pairs of numbers which total 100

• Total - The result of adding.

Partitioning numbers practically can be useful initially in this lesson however pupils should be encouraged to visualise and work more abstractly as they become more confident in generalising about complements to 100
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).

## Starter quiz

### 6 Questions

Q1.
What is the total of 60 and 40?
110
101
Q2.
Which of these 2-digit numbers is a multiple of ten?
17
35
65
Q3.
What is 100 subtract 4?
6
6 tens
104
94
Q4.
100 = 92 +
Correct Answer: 8, 8, eight, 8 ones
Q5.
Jacob has 75 football cards and wants 100 football cards. How many more football cards does he need?
Q6.
100 subtract equals 97?
30
9
13

## Exit quiz

### 6 Questions

Q1.
Which one is not a complement to 100?
32 + 68
35 + 65
Q2.
What is the total of 67 + 33?
Correct Answer: 100, one hundred, 1 hundred, hundred
Q3.
Match the compliments to 100

75

67

56

4

Q4.
What do you add to 71 to make 100?
39