Place value detectives

Overview

In this lesson you will explore two-digit numbers by analysing the tens and ones, comparing numbers, and explaining your thinking using place value. Students use hands-on representations to support understanding.

Learning intentions

• WALT (We Are Learning To) explore and compare two-digit numbers using place value.
• Students will analyse a number by identifying its tens and ones.
• Students will explain which number is greater/less and why.

Success criteria

• I can tell how many tens and ones are in a two-digit number.
• I can build a two-digit number using base-ten materials or place value cards.
• I can compare two two-digit numbers and justify my answer using tens and ones.
• I can use a number line to show where a number sits between tens.

Curriculum links

• Place value understanding for two-digit numbers (tens and ones).
• Comparing and ordering whole numbers using place value.
• Developing number sense through representing numbers in different ways.
• Reasoning and communicating mathematical thinking using everyday and mathematical language.

Lesson structure (30 minutes)

1. 3 minutes – Warm-up (Number talk) Display two two-digit numbers (e.g., 34 and 41). Ask: “Which number has more tens? Which has more ones? Who is greater and why?” Students turn-and-talk, then share.

2. 7 minutes – Model with concrete and visuals Place value cards for tens and ones (or base-ten blocks) are shown. Teacher models analysing a number (e.g., 27):

• “Two tens means 20. Seven ones means 7. So 27 is 20 + 7.” Repeat quickly with a second number (e.g., 35) with students prompting.

3. 8 minutes – Hands-on practice (Build, analyse, explain) Students in pairs choose number cards. For each card they:

• build it with base-ten blocks/place value counters,
• record tens and ones on a small recording sheet,
• say a sentence: “This number has __ tens and __ ones, so it is __.” Teacher circulates, prompting with: “What does the tens digit tell you?” and “How do you know?”

4. 7 minutes – Compare using number sentences Teacher writes comparison frames:

• “__ is greater than __ because…”
• “__ and __ are close because both have __ tens…” Pairs compare two new number cards and complete one sentence. Students must use place value language (tens first, then ones). Include a quick whole-class share of one example.

5. 3 minutes – Guided number-line check Using a shared visual number line marked in tens, teacher asks students to place two-digit numbers between tens (e.g., place 48 between 40 and 50). Students point and explain: “It’s in the 40s because it has 4 tens.”

6. 2 minutes – Exit ticket (Quick assessment) Each student completes a one-question task:

• “Write the tens and ones for 2-digit number __. Circle the greater number between __ and __, and explain using tens/ones.”

Resources

• Base-ten blocks (tens rods and ones cubes) or place value counters
• Place value cards labelled Tens and Ones (or digit cards for tens and ones)
• Two-digit number cards (range suited to Year 1–2 expectations)
• Number lines marked in tens (0–100) with optional smaller tick marks for ones
• Comparison sentence strips (e.g., “is greater than because…”)
• Recording sheets: tens/ones table and a space for one sentence explanation
• Sticky notes or mini whiteboards for exit ticket responses
• Visual supports: example “20 + 7 = 27” (teacher model) and word bank (tens, ones, greater, less)

Assessment

• Teacher observation during build-and-explain: can students correctly identify tens and ones?
• Review exit tickets: place value accuracy and the quality of comparison explanations.
• Listening during number talk and comparison sharing: using tens/ones reasoning, not guessing.

Differentiation

• Support (lower levels / visual number lines): provide a number line with highlighted tens (e.g., 30–40) and pre-made tens rods; students place ones to locate the exact number.
• Support for EALD: sentence frames with word bank; allow pointing to tens/ones materials while speaking; pair with a supportive peer; use consistent language (“tens first, then ones”).
• SEN/ND students: reduce cognitive load by using fewer comparison steps (one comparison per turn); offer worked examples; allow extra processing time and clear, short instructions.
• Extension (advanced learners): students create a “place value comparison game” using two-digit cards, rules such as “Winner is the player who first explains the greater number using tens and ones,” and include at least one wildcard card that changes the tens (e.g., swap tens digit only).