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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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Share activities with pupils
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.

Download all resources
Share activities with pupils

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).

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Starter quiz

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6 Questions

Q1.
Tick the number facts that make 10.
4 + 7
Correct answer: 2 + 8
Correct answer: 9 + 1
Correct answer: 7 + 3
Correct answer: 6 + 4
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.
An image in a quiz
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
Correct answer: 70
17
170
Q6.
What are the missing numbers that the nine would need to be partitioned into to bridge 10 for this example.
An image in a quiz
3 and 6
2 and 7
Correct answer: 4 and 5
1 and 8

Exit quiz

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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?
Correct answer: 0.4 and 0.6
0.2 and 0.7
0.9 and 0.2
Correct answer: 0.3 and 0.7
Correct answer: 0.5 and 0.5
Q4.
Use a known number fact to help you solve: 1 − 0.3 =
Correct Answer: 0.7, seven tenths, zero point seven, nought point seven
Q5.
Fill in the missing number for the equation represented by the number line.
An image in a quiz
Correct Answer: 0.9, zero point nine, nine tenths, nought point nine
Q6.
Fill in the missing number: ___ − 0.7 = 0.8
Correct Answer: 1.5