Lesson Notes By Weeks and Term v5 - Grade 12

Lesson Video

This page supports the lesson note with a companion video and a short classroom-ready summary.

For class groups and homework, share this lesson page so learners also get the summary, objectives, and full lesson context.

Performance objectives

• Calculate distances and areas using scale.
• Interpret symbols and keys on maps and plans.
• Determine direction using compasses and bearings.
• Analyse and compare different types of maps.
• Use maps and plans to solve practical problems.

Lesson summary

This week, we delve into the crucial topic of interpreting and utilizing maps, plans, and other visual representations to make informed decisions. In South Africa, this skill is vital for navigating diverse environments, understanding urban planning, interpreting building plans, and making sound financial decisions related to property. From understanding the layout of a complex shopping mall to interpreting a detailed building plan for a new RDP house, the ability to extract information and make inferences from these representations is invaluable.

Lesson notes

2.1 Understanding Scale: Scale is the ratio that represents the relationship between a distance on a map or plan and the corresponding distance on the ground. It is crucial for accurately calculating real-world distances from a representation.

Scale can be expressed in three main ways: Ratio Scale: Expressed as a ratio, e.g., 1:

5

0

0

0

0. This means that 1 unit on the map represents 50000 of the same units on the ground.

Word Scale: Expressed in words, e.g., "1 cm represents 1 km." Linear Scale (Graphic Scale): A line divided into segments, representing ground distances. This is useful because it remains accurate even if the map is enlarged or reduced.

Example 1: Calculating Distance using Ratio Scale A map has a scale of 1:

2

0

0

0

0. Two landmarks are 7.5 cm apart on the map. What is the actual distance between them on the ground, in kilometers?

Step 1: Understand the scale: 1 cm on the map = 20000 cm on the ground.

Step 2: Calculate the ground distance in centimeters: 7.5 cm 20000 = 150000 cm Step 3: Convert centimeters to meters: 150000 cm / 100 = 1500 meters Step 4: Convert meters to kilometers: 1500 meters / 1000 = 1.5 km Therefore, the actual distance between the landmarks is 1.5 km.

Example 2: Calculating Area using Scale A rectangular park measures 5 cm by 8 cm on a plan with a scale of 1:

5

0

0. What is the actual area of the park in square meters?

Step 1: Understand the scale: 1 cm on the plan = 500 cm on the ground.

Step 2: Calculate the actual length and width in centimeters: Length: 5 cm 500 = 2500 cm Width: 8 cm 500 = 4000 cm Step 3: Convert centimeters to meters: Length: 2500 cm / 100 = 25 meters Width: 4000 cm / 100 = 40 meters Step 4: Calculate the area in square meters: Area = Length Width = 25 m * 40 m = 1000 square meters Therefore, the actual area of the park is 1000 square meters. 2.2 Understanding Map Symbols and Keys (Legends): A map key (or legend) explains the symbols used on a map or plan. These symbols represent various features like roads, rivers, buildings, forests, hospitals, schools, and points of interest. Understanding the key is essential for correctly interpreting the information presented on the map. Pay close attention to the specific symbols used, as they can vary between different maps and plans. In the South African context, you might find symbols indicating specific types of housing (e.g., RDP housing), clinics, or community centers.

Example: A map key might show a blue line representing a river, a black line representing a road, a red cross representing a hospital, and a small square representing a school. 2.3 Determining Direction and Orientation: Maps are oriented to show direction, usually with North at the top. Compass directions (North, South, East, West) and bearings (angles measured clockwise from North) are used to specify direction.

Compass Directions: Useful for general orientation.

Bearings: More precise for navigation. Bearings are written as three-digit numbers (e.g., 045° for Northeast, 180° for South).

Example: If a landmark is located on a bearing of 135° from your current position, it is located Southeast of you. 2.4 Analyzing and Comparing Different Representations: Different types of maps and plans provide different levels of detail and are suitable for different purposes.

For example: Road Maps: Focus on road networks and are useful for planning journeys.

Topographic Maps: Show elevation changes and landforms and are useful for hiking and environmental planning.

Building Plans: Show the layout and dimensions of buildings and are essential for construction.

Satellite Images: Provide a broad overview of an area and are useful for identifying land use patterns. It's important to consider the purpose of each representation and its limitations when interpreting information. For example, a road map might not show the exact location of all buildings, while a building plan won't provide information about surrounding terrain. Guided Practice (With Solutions)

Question 1: A map of Gauteng has a scale of 1:

1

5

0

0

0

0

0. The distance between Johannesburg and Pretoria on the map is 3.5 cm. What is the actual distance between the two cities in kilometers?

Solution: Step 1: Understand the scale: 1 cm on the map = 1500000 cm on the ground.

Step 2: Calculate the ground distance in centimeters: 3.5 cm 1500000 = 5250000 cm Step 3: Convert centimeters to kilometers: 5250000 cm / 100 / 1000 = 52.5 km Answer: The actual distance between Johannesburg and Pretoria is 52.5 km.

Question 2: A rectangular plot of land is represented on a plan with a scale of 1:

2

0

0. On the plan, the plot measures 12 cm long and 8 cm wide. Calculate the actual area of the plot in square meters.

Solution: Step 1: Understand the scale: 1 cm on the plan = 200 cm on the ground.