Add and subtract to and from a 3-digit number bridging 100
Lesson details
Learning outcome
I can add and subtract to and from a 3-digit number bridging 100.
Key learning points
- Addition and subtraction calculations can represent counting on and back over the 100s boundary.
- When you count on in tens, sometimes the 10s digit only changes and sometimes the 100s digit changes.
- When you count back in tens, sometimes the 10s digit only changes and sometimes the 100s digit changes.
Keywords
Bridging - A mental strategy which uses addition or subtraction to cross a number boundary.
Partition - Splitting an object or value down into smaller parts.
100s boundary - The point at which numbers change into 100s numbers, or from one set of hundreds to another.
Common misconception
Pupils may partition numbers incorrectly when adding or subtracting across a 100s boundary.
Encourage pupils to add or subtract to first the 100s number, using number pairs that total 10 or 100.
Teacher tip
Pupils may find base ten blocks or interlocking cubes helpful in representing the calculations and partitioning numbers. Encourage them to use number lines alongside these manipulatives so that they develop confidence in representing their thinking.
Licence
Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.40 can be partitioned into 30 and
Q2.How can 60 be partitioned into two parts?
Q3.95 + = 100
Q4.150 + = 200
Q5.300 − 6 =
Q6.The total height of Peter and the boxes is 300 cm. Peter is 80 cm tall. How high are the boxes?
Assessment exit quiz
6 Questions
Q1.How would you partition 6 to calculate 97 + 6 efficiently?
Q2.How would you partition 7 to calculate 105 − 7?
Q3.Which calculations cross a 100s boundary?
Q4.220 − 30 =
Q5.Use the number line to complete the calculation. 370 + = 420
Q6.Use the number line to complete the calculation. 550 − = 480
To help you plan your 3 maths lesson on: Add and subtract to and from a 3-digit number bridging 100, download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your 3 maths lesson on: Add and subtract to and from a 3-digit number bridging 100, download all teaching resources for free and adapt to suit your pupils' needs.
The starter quiz will activate and check your pupils' prior knowledge, with versions available both with and without answers in PDF format.
We use learning cycles to break down learning into key concepts or ideas linked to the learning outcome. Each learning cycle features explanations with checks for understanding and practice tasks with feedback. All of this is found in our slide decks, ready for you to download and edit. The practice tasks are also available as printable worksheets and some lessons have additional materials with extra material you might need for teaching the lesson.
The assessment exit quiz will test your pupils' understanding of the key learning points.
Our video is a tool for planning, showing how other teachers might teach the lesson, offering helpful tips, modelled explanations and inspiration for your own delivery in the classroom. Plus, you can set it as homework or revision for pupils and keep their learning on track by sharing an online pupil version of this lesson.
Explore more key stage 2 maths lessons from the Representing 3-digit numbers, comparing and positioning on number lines unit, dive into the full primary maths curriculum, or learn more about lesson planning.