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examBoard: Cambridge
examType: IGCSE
lessonTitle: Number Operations and Calculations
Geography isn't just about maps and places - it involves numbers too! Being able to work with numbers helps us make sense of geographical patterns and processes. In this session, we'll explore the key mathematical skills you need for your iGCSE Geography exams and coursework.
Key Definitions:
Mathematical skills help you to:
In your iGCSE Geography exams, you'll need to:
Let's start with the four basic operations you'll need to use in geography:
Geographical applications:
Example: If a city had 250,000 people in 2010 and 275,000 in 2020, the population increase is 275,000 - 250,000 = 25,000 people.
Geographical applications:
Example: If 35mm of rain falls in one week, the average daily rainfall is 35 ÷ 7 = 5mm per day.
These calculations help us compare data and understand relationships between different values.
Percentages are really useful in geography for comparing data and showing change over time.
To calculate percentage change:
Formula: ((New value - Original value) ÷ Original value) × 100
Example: If population grows from 10,000 to 12,500:
((12,500 - 10,000) ÷ 10,000) × 100 = (2,500 ÷ 10,000) × 100 = 0.25 × 100 = 25% increase
To find what percentage one value is of another:
Formula: (Value ÷ Total) × 100
Example: If 15 million people out of a country's 60 million population live in urban areas:
(15 ÷ 60) × 100 = 0.25 × 100 = 25% live in urban areas
Ratios show the relationship between two or more values and are written using colons (e.g., 3:1).
Example: If a country has 30 million males and 32 million females, the gender ratio is 30:32, which can be simplified to 15:16.
Averages help us understand typical values in a dataset. There are three main types of averages you need to know:
The mean is calculated by adding all values and dividing by the number of values.
Formula: Sum of all values ÷ Number of values
Example: Mean annual rainfall
If monthly rainfall figures (in mm) are: 60, 45, 50, 55, 70, 30, 25, 35, 40, 65, 75, 60
Mean = (60+45+50+55+70+30+25+35+40+65+75+60) ÷ 12 = 610 ÷ 12 = 50.8mm
The middle value when all data is arranged in order.
How to find it: Arrange values in order and find the middle value (or average of two middle values if there's an even number).
Example: For temperatures: 12°C, 15°C, 18°C, 22°C, 25°C
Median = 18°C (middle value)
The most frequently occurring value in a dataset.
How to find it: Identify which value appears most often.
Example: For land use categories in a survey: Residential, Commercial, Residential, Industrial, Residential, Green space
Mode = Residential (appears 3 times)
Mean: Best for continuous data like rainfall or temperature, but can be skewed by extreme values.
Median: Useful when data has extreme values that might distort the mean.
Mode: Helpful for categorical data like land use types or for identifying the most common value.
Rates of change help us understand how quickly something is changing over time.
A rate is calculated by dividing the amount of change by the time period over which the change occurred.
Formula: (Population change ÷ Time period) × 100
Example: If a country's population increases from 50 million to 56 million over 10 years:
Annual growth rate = ((56 - 50) ÷ 10) = 0.6 million per year
As a percentage: (0.6 ÷ 50) × 100 = 1.2% per year
Nigeria is experiencing rapid population growth. In 1950, its population was about 33 million. By 2020, it had reached approximately 206 million.
Calculation: Total growth = 206 - 33 = 173 million
Time period = 70 years
Average annual growth = 173 ÷ 70 = 2.47 million people per year
This represents one of the fastest population growth rates in the world, creating both challenges and opportunities for development.
Mathematical skills are essential tools for geographers. They help us analyse data, identify patterns and understand geographical processes. In your iGCSE Geography course, you'll need to apply these skills to a range of topics including population, climate, economic development and environmental change.
Remember that practice makes perfect! The more you work with geographical data, the more confident you'll become with these mathematical skills.
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