🎯 Learning Objectives
By the end of this lesson, you should be able to:
- Explain what a scale drawing is.
- Find a drawing length by dividing a real length by the scale value.
- Draw straight lines to a stated scale.
- Check that a drawing remains proportional.
🤔 Start with the Idea
A scale drawing is an accurate smaller or larger version of a real object. Every length is changed by the same scale, so the shape stays proportional.
📖 From Real Length to Drawing Length
When 1 cm represents 2 m, every 2 m in real life becomes 1 cm on the drawing.
For a 10 m wall:
🎮 Explore the Scale
Change the map or drawing length and the scale value. Notice how the real distance changes proportionally.
🧠 Let’s Think Together
A rectangular garden is 12 m long and 8 m wide. Draw it using 1 cm represents 2 m.
Length on drawing: 12 ÷ 2 = 6 cm.
Width on drawing: 8 ÷ 2 = 4 cm.
Draw a 6 cm by 4 cm rectangle and write the scale below it.
✏️ Practice Questions
Build confidence- At 1 cm = 3 m, find the drawing length for 18 m.
- A room is 9 m by 6 m. Drawings use 1 cm = 1.5 m. Find both drawing dimensions.
- Why must every side use the same scale?
✅ Check your answers
- 6 cm
- 6 cm by 4 cm
- To preserve the correct proportions
⚠️ Common Mistakes
- Using different units on the two sides of a ratio scale.
- Multiplying when the question requires division, or dividing when it requires multiplication.
- Leaving out the unit or using a linear unit for an area.
- Rounding too early in a multi-step calculation.
🎯 Exam Focus
Write what the scale means before calculating. Show unit conversions clearly, keep full calculator values until the final step, and include the correct unit in the answer.
📌 One-Minute Summary
- A scale connects a drawing or model to the corresponding real object.
- Use multiplication when moving from a drawing measurement to a real measurement.
- Use division when working backwards from real size to drawing size.
- Ratio scales require the same unit on both sides.
- Area changes by the square of the linear scale factor.