Population Density Is a Ratio
Divide people by area to calculate the average population density in the supplied examples.
About 15 minutes, plus any extended practice
Supplied materials
- Paper and pencil; drawing or spoken answers are welcome.
- Topic notes: 10 people per square kilometre: the ratio for the stated population and area. 20 people per square kilometre: the ratio for the stated population and area. 50 people per square kilometre: the ratio for the stated population and area. 100 people per square kilometre: the ratio for the stated population and area.
- Original exercise cards: Fictional area has 100 people across 10 square kilometres. / Fictional area has 100 people across 5 square kilometres. / Fictional area has 500 people across 10 square kilometres. / Fictional area has 500 people across 5 square kilometres. / Fictional area has 400 people across 20 square kilometres. / Fictional area has 150 people across 3 square kilometres. / Fictional area has 800 people across 8 square kilometres. / Fictional area has 200 people across 20 square kilometres.
Learn the idea
Population density compares people with area: people divided by the stated land area. Total population and density answer different questions. Two places can have the same population but different densities. These exercise figures are fictional; use the same area unit when comparing them.
10 people per square kilometre: the ratio for the stated population and area. 20 people per square kilometre: the ratio for the stated population and area. 50 people per square kilometre: the ratio for the stated population and area. 100 people per square kilometre: the ratio for the stated population and area.
Divide the number of people by the area. Keep the answer in people per square kilometre. Read the notes and the word cards. You can write, draw or say your answer.
- Read the four notes. Find the words 10 people per square kilometre, 20 people per square kilometre, 50 people per square kilometre, 100 people per square kilometre.
- Divide the number of people by the area. Keep the answer in people per square kilometre.
- Read the worked answer. Then try the other cards and explain which words helped you choose.
- Choose two different examples: one for 10 people per square kilometre and one for 20 people per square kilometre. Explain how their clues differ.
See the method in action
Fictional area has 100 residents across 10 square kilometers. Density equals people divided by area: 100 ÷ 10 = 10 people per square kilometer. This is a regional average, not a count of ten residents in every actual square. To compare another place, divide its population by its own area using the same units. A larger population total does not by itself mean higher density.
Check your reasoning
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Helpful tips
- Divide the number of people by the area. Keep the answer in people per square kilometre.
- If you are unsure, ask an adult to read the card again. Match what this card says; do not add a new event or detail.
See the answer and explanation
20 people per square kilometre
Divide people by area: 100 ÷ 5 = 20. The density is 20 people per square kilometre. This is an average across the stated area, not a count in every square.
Take it further
New card: “Fictional area has 200 people across 20 square kilometres.” Match it with a note, then point to or say the words that helped. Check: Divide people by area: 200 ÷ 20 = 10. The density is 10 people per square kilometre. This is an average across the stated area, not a count in every square.
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More practice: try new cases
Choose an answer for each problem. Explain your method on paper, then use the feedback to decide what to revisit.
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Check the subject sources
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