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Compound Interest (Using Formula) — Revision Notes

ICSE · Class 9 · Mathematics

Compound Interest (Using Formula) revision notes for ICSE Class 9 Mathematics: 4 topics in quick points. Part of the ICSE Class 9 Mathematics syllabus.

37 questions25 flashcards4 formulas & key relations5 concepts

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A labeled diagram explaining the components of the compound interest formula A = P(1 + r/100)^n when interest is compounded yearly.
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Key Topics to Revise

1

1. Core idea and direct formula

  • Amount means the total money after interest is added.
  • Principal means the original sum of money.
  • Compound interest is the extra money earned over the principal.
2

2. Amount when rates are different in successive years

  • When the rate changes from year to year, each year is treated separately.
  • The first year's amount becomes the principal for the next year.
  • Multiply the yearly growth factors in order.
3

3. Finding principal, rate, and time

  • The formula can be rearranged to find principal, rate, or time.
  • If amount and time are known, principal can be found by dividing back through the growth factor.
  • If principal and amount are known, the rate can be found by comparing the growth factor to a known power.
4

4. Age and sharing problems

  • Age-based sharing problems depend on the number of years left until a common target age.
  • Each person's investment grows for a different number of years.
  • The person with fewer years to grow needs a larger initial share if both final amounts are equal.

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Full Notes

Key Concepts

The amount after n yearsCompound interest can be found directlyWhen the rate changes from yearFor interest compounded halfIf compounding is yearly but time

Frequently Asked Questions

What are the important topics in Compound Interest (Using Formula) for ICSE Class 9 Mathematics?
Key topics in Compound Interest (Using Formula) include Core idea and direct formula, Amount when rates are different in successive years, Finding principal, rate, and time, Age and sharing problems. Study these first, then practise questions on each for Class 9 exams.
How should I revise Compound Interest (Using Formula) for Class 9 exams?
Learn the core ideas first, then work through the 37 practice questions on Compound Interest (Using Formula). Revise definitions regularly and use flashcards for quick recall before the exam.

Sources & Official References

Content is aligned to the official syllabus. Refer to the board website for the latest curriculum.

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All ICSE Class 9 Mathematics Revision Notes

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