New
New
Year 5

# Use known facts and mental strategies to calculate with decimal numbers within and across a whole

I can use known facts and mental strategies to calculate with decimal numbers within and across a whole.

New
New
Year 5

# Use known facts and mental strategies to calculate with decimal numbers within and across a whole

I can use known facts and mental strategies to calculate with decimal numbers within and across a whole.

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## Lesson details

### Key learning points

1. If you know that 5 + 2 is equal to 7 then 5 tenths + 2 tenths is equal to 7 tenths so 0.5 + 0.2 = 0.7
2. Use known facts and unitising to add tenths.
3. Bridging 10 strategies with whole numbers can be applied when the tenths bridge one whole.

### Common misconception

Pupils record missing part equations incorrectly.

Encourage children to match the equation to a representation identifying which number represents the wholes and which represent parts.

### Keywords

• Number facts - Simple calculations using two numbers are known as number facts. For example 2 + 4 = 6

• Bridging - Bridging is a mental strategy which uses addition or subtraction to cross a number boundary.

Use the language of unitising to support pupils each time. For example: I know 10 ones minus 3 ones is equal to 7 ones so 10 tenths minus 3 tenths is equal to 7 tenths.
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.
Tick the number facts that make 10.
4 + 7
Q2.
Ten tenths are equal to
Correct Answer: 1, 1 whole, a whole, one, whole
Q3.
I know 7 − 5 = 2 so 700 − 500 =
Correct Answer: 200, 200, 2 hundred
Q4.
Tick all of the equations that can represent this part-part-whole model.
Correct answer: 6 + 4 = 10
10 = 6 − 4
6 = 10 + 4
Correct answer: 6 = 10 − 4
Correct answer: 10 − 6 = 4
Q5.
I know 12 − 5 = 7 so 120 − 50 =
7
17
170
Q6.
What are the missing numbers that the nine would need to be partitioned into to bridge 10 for this example.
3 and 6
2 and 7
1 and 8

## Exit quiz

### 6 Questions

Q1.
I know 3 + 6 = 9 so 0.3 + 0.6 =
Correct Answer: 0.9, zero point nine, nought point nine, nine tenths, 9 tenths
Q2.
I know 8 − 5 = 3 so 0.8 − 0.5 =
Correct Answer: 0.3, zero point three, nought point three, 3 tenths
Q3.
Which of these pairs of numbers sum to make 1?