Add and subtract one to or from a two-digit number within a decade
Lesson details
Learning outcome
I can add and subtract 1 to and from a 2-digit number within a decade.
Key learning points
- Finding one more is the same as adding 1. Finding one less is the same as subtracting 1
- Numbers that are one more or one less than each other have a difference of one.
Keywords
One more - The number that is one more than another is the result of adding 1 to that number
One less - The number that is one less than another is the result of subtracting 1 from that number
Difference - The result of subtracting one number from another. How much one number differs from another.
Common misconception
The language of one more or one less than can confuse children, so 55 is one more than ? may be interpreted as 55 plus 1
Encourage children to articulate and explain in full sentences alongside number lines to support the understanding of the different ways to articulate the concept. Use stem sentences to support with this and display them around the classroom.
Teacher tip
Avoid calculations which involve regrouping at this point. Use part-part-whole models to teach commutativity and inverse. Allow children the opportunity to explore these patterns with familiar representations such as number lines and base ten equipment.
Licence
Lesson video
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Prior knowledge starter quiz
6 Questions
Q1.Which picture shows one less than 12?
Q2.Which number would complete the part-part-whole model correctly?
Q3.Fill in the missing number. ___ is one more than 8
Q4.Find the missing number.
Q5.Alex is thinking of two numbers which have a difference of 1 One of the numbers is 15 What could the other number be?
Q6.Find the missing number.
Assessment exit quiz
6 Questions
Q1.Use a number line or one hundred square to help you find the missing number.
Q2.Which picture shows one less than 37?
Q3.Which number would complete the part-part-whole model correctly?
Q4.Use the part-part-whole model to help you complete the equation. 43 - = 42
Q5.Complete the stem sentence. is one more than 76
Q6.Tick the equations that would represent, '25 is one less than 26'
To help you plan your 2 maths lesson on: Add and subtract one to or from a two-digit number within a decade, download all teaching resources for free and adapt to suit your pupils' needs...
To help you plan your 2 maths lesson on: Add and subtract one to or from a two-digit number within a decade, 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 1 maths lessons from the Adding and subtracting ones and tens to and from 2-digit numbers unit, dive into the full primary maths curriculum, or learn more about lesson planning.