Corbettmaths Style Area of Rectangles Guide for Grade 3

Complete Corbettmaths-style guide to area of rectangles: comprehensive lessons, practice exercises, and step-by-step solutions with visual explanations.

Corbettmaths Style Exercises
1 Basic Rectangle Areas
Calculate Areas
Find the area of these rectangles: 5 cm × 3 cm, 7 cm × 4 cm, 6 cm × 6 cm
Key Concepts:

Rectangle: A four-sided shape with four right angles and opposite sides equal

Area: The amount of space inside a 2D shape, measured in square units

Formula: Area = length × width

Corbettmaths Method:
  1. Identify dimensions: Find the length and width of the rectangle
  2. Write the formula: Area = length × width
  3. Substitute values: Replace variables with actual measurements
  4. Calculate: Multiply the length by the width
  5. Include units: Add square units to your answer
Example 1
5 × 3 = 15 cm²
Example 2
7 × 4 = 28 cm²
Example 3
6 × 6 = 36 cm²
Step 1: Rectangle 5 cm × 3 cm

Area = length × width = 5 × 3 = 15 cm²

Step 2: Rectangle 7 cm × 4 cm

Area = length × width = 7 × 4 = 28 cm²

Step 3: Square 6 cm × 6 cm

Area = length × width = 6 × 6 = 36 cm²

Areas: 15 cm², 28 cm², 36 cm²
Solutions:

Rectangle 5×3: 15 cm², Rectangle 7×4: 28 cm², Square 6×6: 36 cm²

Corbettmaths Rules:

• Always write the formula first

• Substitute values systematically

• Include square units in your final answer

• Show all steps clearly

2 Missing Dimension Problems
Find Missing Dimensions
A rectangle has an area of 24 cm² and a width of 4 cm. What is its length?
Inverse Problems:

When area and one dimension are known: Use division to find the missing dimension

Rearrange the formula: If Area = length × width, then length = Area ÷ width

Given
Area = 24 cm², Width = 4 cm
Formula
Length = A ÷ W
Result
Length = 6 cm
Step 1: Write down what you know

Area = 24 cm², Width = 4 cm, Length = ?

Step 2: Rearrange the formula

Area = length × width → length = Area ÷ width

Step 3: Substitute known values

Length = 24 ÷ 4

Step 4: Calculate the answer

Length = 6 cm

Step 5: Verify your answer

Check: 6 × 4 = 24 cm² ✓

Length = 6 cm
Solution:

The length of the rectangle is 6 cm

Inverse Problem Rules:

• Identify what is given and what is asked

• Rearrange the formula to solve for the unknown

• Use division when finding missing dimensions

• Always verify your answer by substituting back

3 Word Problems
Real-World Application
Sarah wants to carpet her rectangular bedroom. The room is 5 feet long and 4 feet wide. How many square feet of carpet does she need?
Word Problem Strategy:

Read carefully: Identify the shape and measurements given

What is asked: Determine if you need to find area, length, or width

Apply formula: Use the appropriate area formula

Given
Length = 5 ft, Width = 4 ft
Formula
Area = l × w
Result
20 ft²
Step 1: Identify the shape and measurements

Rectangular bedroom: length = 5 ft, width = 4 ft

Step 2: Determine what is being asked

"How many square feet of carpet" means find the area

Step 3: Apply the area formula

Area = length × width = 5 × 4

Step 4: Calculate the area

Area = 20 square feet

Step 5: State the answer in context

Sarah needs 20 square feet of carpet

Sarah needs 20 ft² of carpet
Solution:

Sarah needs 20 square feet of carpet for her bedroom

Word Problem Rules:

• Read the problem carefully and underline key information

• Identify the shape and measurements

• Determine what is being asked

• Apply the appropriate formula

• State your answer in the context of the problem

Corbettmaths Style Summary
Area = length × width
Core Formula
Basic Formula
A = l × w
Area equals length times width
Finding Length
l = A ÷ w
Length equals area divided by width
Finding Width
w = A ÷ l
Width equals area divided by length
Corbettmaths Definitions:

Area: The amount of space inside a 2D shape, measured in square units

Rectangle: A quadrilateral with four right angles and opposite sides equal

Square: A special rectangle where all four sides are equal

Square Units: Units used to measure area (cm², m², ft², in²)

Dimensions: The measurements of length and width

Corbettmaths Problem-Solving Method:
  1. Read the question carefully - Identify what is given and what is asked
  2. Write down the relevant formula - Area = length × width
  3. Substitute the known values - Replace variables with measurements
  4. Calculate the result - Perform the multiplication or division
  5. Include the correct units - Always add square units
  6. Check your answer - Verify it makes sense in context
Tip 1: Always write the formula before substituting values.
Tip 2: Include square units in your final answer.
Tip 3: Check that your answer is reasonable for the given dimensions.
Tip 4: For missing dimensions, use division: Area ÷ known dimension.
Tip 5: Draw a diagram to visualize the problem when needed.
Common Mistakes: Forgetting square units, adding instead of multiplying, misreading dimensions.
Memorization Tip: "Area = Length × Width" - always multiply!
Corbettmaths Rules:

• Area of rectangle: A = l × w

• Area of square: A = s²

• Finding length: l = A ÷ w

• Finding width: w = A ÷ l

• Always include square units in your answer

• Show all working steps clearly

Corbettmaths Practice Problems
Area Calculations
Practice problems with various dimensions:
Rectangle 3×4: 12 cm²
Rectangle 5×2: 10 cm²
Square 6×6: 36 cm²
Rectangle 7×3: 21 cm²

Corbettmaths Practice Insight: Systematic approach leads to accurate results!

  • Rectangle 3×4 = 12 cm²
  • Rectangle 5×2 = 10 cm²
  • Square 6×6 = 36 cm²
  • Rectangle 7×3 = 21 cm²

Questions & Answers

Question: What makes Corbettmaths style different from regular math problems?

Answer: Corbettmaths style emphasizes clear, step-by-step working and systematic approaches:

  • Clear working: Show every step of your solution
  • Formula first: Always write the relevant formula before substituting values
  • Systematic approach: Follow a consistent method for all problems
  • Verification: Check your answers when possible
  • Clear presentation: Organize your work neatly

This method helps prevent mistakes and makes it easier to identify where errors occur.

The systematic approach builds good mathematical habits that will serve you well in future studies.

Question: Do I really need to write the formula every time in Corbettmaths style?

Answer: Yes, writing the formula is a key part of the Corbettmaths approach for several important reasons:

  • Clarifies thinking: It reminds you which formula to use
  • Shows understanding: Demonstrates you know the correct method
  • Prevents errors: Helps avoid using the wrong formula
  • Earns marks: Shows your method in assessments
  • Good habit: Builds discipline for more complex problems

Even if you know the answer, writing the formula ensures you're following the correct process.

This systematic approach becomes increasingly valuable as math problems become more complex.

It's better to write the formula and get the method mark than to skip it and risk losing points!

Question: How can I practice Corbettmaths style area problems effectively?

Answer: Here's an effective approach to practicing Corbettmaths style area problems:

  • Start with basics: Master simple rectangle areas first
  • Follow the method: Always use the 6-step Corbettmaths approach
  • Write everything down: Don't do calculations mentally
  • Check your work: Verify each answer makes sense
  • Practice variety: Work on different types of problems

Daily practice routine:

  • Solve 3-5 problems daily using the full method
  • Review any mistakes and understand why they occurred
  • Gradually increase difficulty as you improve
  • Time yourself to build speed while maintaining accuracy

The key is consistency - practice regularly using the systematic approach, and it will become natural over time!