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examBoard: Cambridge
examType: IGCSE
lessonTitle: Range, Decimals and Fractions
Geography isn't just about maps and places it's also about understanding numbers that help us make sense of our world! In this session, we'll explore three key mathematical skills that are essential for your iGCSE Geography studies: range, decimals and fractions.
Key Definitions:
Mathematical skills help geographers analyse patterns, compare places and understand changes over time. Whether you're studying climate data, population statistics, or economic development, these skills will help you interpret and present geographical information clearly and accurately.
In your iGCSE Geography exam, you'll need to interpret data presented in tables and graphs, calculate percentages and averages and understand the significance of numbers in geographical contexts. These skills are tested throughout the paper, so mastering them is essential!
Range is a simple but powerful way to show the spread or variation in a set of data. It helps geographers identify extremes and understand the extent of differences in their data.
To calculate the range, simply subtract the lowest value from the highest value in your data set:
Range = Highest value - Lowest value
Imagine you're studying the climate of Cairo, Egypt. The highest monthly average temperature is 35°C (July) and the lowest is 19°C (January).
Range = 35°C - 19°C = 16°C
This tells us that Cairo experiences a temperature range of 16°C throughout the year.
Calculate daily or annual temperature ranges to compare continental and maritime climates.
Analyse the range of income or HDI values to understand inequality between and within countries.
Examine the range of house prices or population densities across different parts of a city.
Decimals are everywhere in geography! From precise measurements of rainfall (e.g., 56.7mm) to exact coordinates (51.5074°N), understanding decimals is crucial for accurate geographical work.
In geography, you'll often need to understand what decimal places mean:
When studying the Amazon Rainforest's climate, you might record that Manaus receives an average of 2,307.3mm of rainfall annually. The decimal here (0.3mm) represents a very precise measurement that could be important when comparing rainfall patterns across different years or locations.
You'll need to add, subtract, multiply and divide decimals when working with geographical data.
To find the average monthly rainfall, divide the annual total by 12:
2,307.3mm ÷ 12 = 192.275mm per month
You might round this to 192.3mm for clarity.
If a country has an area of 342.5 km² and a population of 76,400:
Population density = 76,400 ÷ 342.5 = 223.1 people per km²
Fractions help us express parts of a whole and are particularly useful when discussing proportions, ratios and distributions in geography.
In geography, you'll commonly work with:
Fractions help us understand how land is used in different areas. For example, in the UK, approximately ⅔ of land is used for agriculture, while about 1/10 is urban development.
When studying global resources, you might learn that about ⅕ of the world's population lives in China, or that approximately ¼ of the Earth's surface is covered by land.
While studying global water resources, you might discover that:
Understanding these fractions helps explain why water scarcity is a critical global issue despite the planet being covered mostly by water.
These mathematical skills aren't just for the classroom they're essential tools for geographical fieldwork and investigations.
Measure river width and depth (in decimals of metres) at different points, then calculate the range to understand how the channel changes downstream.
Record temperatures in different locations (e.g., urban vs. rural), then calculate the range to identify the urban heat island effect.
Express different land uses as fractions or percentages of the total area studied to create a land use map.
Once you've collected and analysed your data using range, decimals and fractions, you'll need to present it effectively.
Use appropriate scales with decimal intervals when creating graphs. For example, a climate graph might show temperature in 0.5°C intervals for precision. When showing proportions, pie charts effectively display fractions of a whole.
When presenting data in tables, be consistent with decimal places. In written analysis, use fractions to make comparisons clear (e.g., "approximately one-third of the population lives in urban areas").
Range, decimals and fractions are fundamental mathematical skills that will help you throughout your geography studies. They allow you to:
In your iGCSE Geography exam, you might be asked to:
Remember to show your working clearly and include appropriate units in your answers!
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