Understanding Teen Numbers

Context and Curriculum Links

Level: First Level (Primary 2, ages 6-7)
Curriculum for Excellence (CfE) Experiences and Outcomes:

• MNU 1-03a: I can use practical materials and visual representations to understand and explain place value in numbers up to 20.
• MNU 1-01a: I can count reliably within 100 and use this skill to develop a understanding of number and number processes.
• Benchmarks: By the end of First Level, learners should be confident identifying numbers to 100, understanding place value in two-digit numbers, and solving practical problems involving these numbers.

Learning Intentions

• To understand and represent teen numbers (10-19) using base ten concepts.
• To develop awareness of tens and units within teen numbers.
• To build confidence in recognising and explaining the structure of these numbers.

Success Criteria

• I can identify the tens and units in teen numbers.
• I can use base ten blocks to represent teen numbers accurately.
• I can explain how teen numbers are made up of one ‘ten’ and some ‘ones’.

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Resources Needed

• Base ten apparatus (ten rods and unit cubes) – 1 set per pair
• Number cards (10–19)
• Individual whiteboards and pens
• Worksheet with teen number visual models and simple questions (independent task)

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Lesson Structure (40 minutes)

1. Introduction & Prior Knowledge Activation (5 mins)

• Begin by orally counting from 1 to 20 as a class.
• Briefly recap numbers 1-9 using fingers or counters. Emphasise: what changes at 10?
• Explain that today we will explore what happens after 9, focusing on the teen numbers.

Teacher Talk: "After 9, we start a new way of counting: the numbers have ‘tens’ and ‘ones’ parts. Let’s see how this works with base ten blocks."

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2. Teacher Input & Modelling (15 mins)

• Show a ten rod (group of 10 units) and explain it as "one group of ten."
• Then show single cubes as "one unit."
• Display the number 13 on a number card.
• Ask: How can we show 13 using tens and ones?
• Model placing one ten rod + 3 unit cubes. Say, "13 is made of 1 ten and 3 ones." Write numerically: 13 = 10 + 3.
• Repeat with 11, 15, 19. Encourage learners to verbalise: "one ten and five ones," etc.
• Use a visual chart illustrating the partition of teen numbers into tens and ones to reinforce.

Key question prompts:

• What does the first digit in 13 mean?
• How many ones do we have?
• Can we see this with blocks?

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3. Guided Practice (10 mins)

• Pair learners with base ten sets and teen number cards.
• Give each pair 3 teen number cards (e.g. 12, 17, 14).
• Ask them to build each number physically with the blocks, saying the number and how many tens and ones it has.
• Circulate and support, encouraging use of correct language.
• After building, invite some learners to show their work and explain their thinking to the class.

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4. Independent Task (8 mins)

• Hand out worksheets with pictures of base ten blocks representing teen numbers and ask learners to:

  1. Identify the number represented.
  2. Write the number.
  3. Partition it into tens and ones (simple sentence e.g., "15 = 1 ten and 5 ones.")

• Alternatively, a matching activity where children draw a line between teen number symbols and their base ten representations.

• Provide whiteboards for learners to try writing their own teen numbers and partitioning with teacher assistance as needed.

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5. Plenary & Assessment (2 mins)

• Invite a quick verbal round of: "What is 1 ten and 6 ones? What number is that?"
• Ask a few children to explain, reinforcing language and confidence.
• Collect worksheets for informal assessment against learning intentions.

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Differentiation & Additional Support

• Support: Allow some children to use the blocks for every number during independent work. Use number lines for those needing more visual support.
• Challenge: Ask more confident pupils to explain how the teens compare to 20 or to explain why we call some numbers ‘teen’.
• Use questioning to deepen understanding for all learners.

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Reflection for Next Steps

• Plan to consolidate with addition and subtraction using teen numbers.
• Develop number talks involving teen numbers and their composition.
• Use real-life contexts to embed place value understanding (e.g., grouping objects in tens and ones).

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This lesson encourages conceptual understanding through concrete materials, language development with familiar terminology, and independence fitted to CfE First Level numeracy experiences.