The Area Formula

Overview

Lesson 4 of 10 in Area and Squared Numbers. Students connect the dimensions of a rectangle to the formula length × width, then apply it to practical and diagram-based problems.

Learning intentions

• WALT use length × width to calculate the area of rectangles.
• WALT identify the length and width of a rectangle.
• WALT record area using appropriate square units.
• WALT explain how multiplication represents the total number of square units.

Success criteria

• I can identify the length and width of a rectangle.
• I can choose multiplication to calculate rectangular area.
• I can show my working clearly.
• I can label my answer in square units, such as cm² or m².

Curriculum links

• Measurement: calculate and compare the area of rectangles using standard square units.
• Number and algebra: use multiplication facts and written or mental strategies to solve problems.
• Mathematical communication: represent, explain and justify mathematical thinking using diagrams, symbols and words.
• Key competencies: thinking; using language, symbols and texts; managing self; participating and contributing.

Lesson structure (45 minutes)

1. 0–5 minutes – Hook and recall: Open with the opening question and area image. Display a rectangle made from square tiles and ask: “How could we find how many tiles cover this shape without counting every tile?” Briefly revisit that area measures the surface covered, not the distance around a shape.

2. 5–13 minutes – Teacher modelling: Use square tiles, a drawn grid and a practical rectangle such as a tabletop. Model rows and columns: 4 rows of 6 squares gives 6 × 4 = 24 square units. Introduce and display area = length × width. Emphasise that either dimension can be used first when multiplying, but both dimensions must be measured in the same unit. Refer to the Perimeter and Area Formula Mat as a visual reference.

3. 13–20 minutes – Guided practice: Work through three examples from the modelled examples and guided questions. Students first identify and highlight the length and width, then write the number sentence and answer with units. Use mini-whiteboards or fingers-up responses so all 29 students participate. Ask: “What does each factor represent?” and “Why is the unit squared?”

4. 20–33 minutes – Supported and independent practice: Distribute the rectangle area practice worksheet. Students complete the first two examples with a partner, then work independently on rectangle diagrams and practical contexts. Circulate, checking that students identify dimensions before multiplying. Run an adult-supported group using tiles, the formula mat and worked examples; accept calculators when the focus is area reasoning rather than multiplication fluency.

5. 33–40 minutes – Challenge and discussion: Invite students who finish confidently to solve missing-side problems: “A rectangle has an area of 36 cm² and a width of 6 cm. What is its length? How do you know?” Students may draw or use tiles. Share different strategies, including inverse multiplication, and return to the challenge and strategy discussion.

6. 40–45 minutes – Plenary and check: Display the final prompt from the exit reflection slide: “A rectangle is 8 m long and 3 m wide. Find and label its area.” Students show the formula, calculation and unit, then explain to a partner what the two numbers mean. Collect a selection of responses for next-lesson planning.

Resources

• the Area Formula teaching and activity slides
• the rectangle area practice worksheet
• the Perimeter and Area Formula Mat
• Square tiles or linking cubes
• Mini-whiteboards, pens and erasers
• Rulers and pencils
• Highlighters for identifying key information
• Calculators for selected learners
• Enlarged worked examples for the supported group

Assessment

• Observe whether students distinguish area from perimeter and identify both dimensions correctly.
• Check worksheet calculations, diagrams, working and square units; give immediate feedback during circulation.
• Use the final problem to identify students needing further support with multiplication, units or the formula.

Differentiation

• Provide a formula mat, square tiles, multiplication supports, enlarged worked examples and a calculator where appropriate. Keep the formula visible throughout the lesson.
• For dyslexic learners, use a clear sans-serif font, generous spacing and colour-highlighted length, width and units. Read all written problems aloud, reduce unnecessary text and allow oral explanations or labelled diagrams.
• For the learner with Down syndrome, pre-teach the routine using concrete tiles, offer one step at a time, use repeated language and provide adult or peer support. Accept matching, pointing, oral or practical demonstrations alongside written work.
• Support EAL learners with labelled diagrams, gestures, sentence frames such as “The length is __. The width is __. The area is __ square __.” Pair students carefully and check understanding without relying only on reading.