Depreciation & Population Growth explained through a friendly whiteboard conversation, examples, visuals, and practice for school students.
Step 1
Notes
Step 2
Formulae
Step 3
Examples
Step 4
Practice
Revise the definition, formulae, important results, and exam method first.
Use the sticky diagram while this dedicated tool is being prepared.
Solve only this concept and let the app adapt from your answers.
You have met the idea. Now open a tiny puzzle, a useful fact, and the next best action.
Continue the journey
Depreciation means a value decreases over time.
Population growth means a population increases over time.
Both topics use repeated percentage change, so they connect closely to compound interest.
Some quantities change by the same percentage again and again.
Population growth is usually modelled as repeated increase.
Depreciation is repeated decrease in value, such as the value of a machine or vehicle going down each year.
For growth, multiply by a factor greater than 1. For depreciation, multiply by a factor less than 1.
This is similar to compound interest because each new value is based on the previous value.
Meaning: The quantity grows by a percentage again and again.
If a population grows by 5% each year, the second year growth is based on the first year's new population.
Meaning: The quantity decreases by a percentage again and again.
Definition: Repeated decrease means each new value is reduced by the same percentage rate.
If a machine depreciates by 10% each year, each year it keeps 90% of its previous value.
Meaning: Population growth means the number of people or organisms increases.
Definition: Population after growth can be found using compound percentage increase.
A population of 10000 growing at 5% becomes 10500 after one year.
Meaning: Depreciation means value decreases over time.
Definition: Depreciated value is the value left after repeated percentage decrease.
A phone worth Rs 20000 depreciating by 20% keeps 80% of its value after one year.
Easy
Question: A population of 5000 increases by 10% in one year. Find the new population.
Medium
Question: A machine worth Rs 30000 depreciates by 10% in one year. Find its value after one year.
Exam-level
Question: A town has population 20000 and grows by 5% per year. Find the population after 2 years.
Using simple percentage change for several years
Why it happens: Repeated change is treated as onime change.
Correct approach: Use the new value from each year for the next year.
Using plus for depreciation
Why it happens: The formula shape is remembered without meaning.
Correct approach: Depreciation uses .
Confusing discount and depreciation
Why it happens: Both reduce value.
Correct approach: Discount reduces sale price once. Depreciation reduces value over time.
Is depreciation a loss?
It is a decrease in value over time. It may lead to a loss when selling, but it is a separate idea.
Why do we use powers in these formulas?
The same percentage change is repeated for several periods.
Can population decrease?
Yes. If the question gives a decrease rate, use the depreciatiotyle formula.
Practise the same concept from this article. Your student profile may guide entitlement and follop recommendations, but it does not replace this concept.