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Which of the following situations does NOT use the compound interest growth pattern ?

Class 8Comparing QuantitiesComparing Quantities
  • AA fixed bank fee of ₹100 charged once a year
  • BBacteria doubling and increasing by a fixed percentage each hour
  • CPopulation of a city increasing by a fixed percent per year
  • DValue of a deposit growing at a fixed annual interest rate

Step-by-Step Solution

A fixed amount added each time is linear (like simple interest), not a fixed percentage of a growing base, so it does not follow the compound growth formula.
Answer: A) A fixed bank fee of ₹100 charged once a year

Key idea: Compound interest — interest on interest

After year 1, interest is added to principal — so year 2's interest is calculated on a LARGER amount, not the original.

****, where A is the final amount after years.
**CI = ** (the total interest earned).

Example: ₹2000 at 5% for 3 years, compounded annually:
- Year 1: Year 2: Year 3:

Direct formula: . CI = 2315.25 − 2000 = 315.25 (vs SI of 300 — compound gives more).

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