ICSE Class 10 Maths: Compound Interest — Formulas & Notes 2026

Simple Interest vs. Compound Interest

• SI = PRT/100; interest calculated on original principal only
• CI: interest added to principal each period; next period's interest calculated on new amount
• CI > SI for same P, R, T when T > 1 year

Compound Interest Formula

• A = P(1 + R/100)ⁿ where A = amount, P = principal, R = rate per period, n = number of periods
• CI = A − P
• Finding P when A, R, n given: P = A / (1 + R/100)ⁿ

Compounding Frequency

• Annual: n = years, R = annual rate
• Half-yearly: n = 2 × years, R = annual rate/2
• Quarterly: n = 4 × years, R = annual rate/4

Depreciation

• Value decreases each year: A = P(1 − R/100)ⁿ (depreciation formula)
• Applications: car price, machine value, population decline
• ICSE: find value after n years; find original cost given depreciated value

Population Growth Problems

• A = P(1 + R/100)ⁿ for constant percentage growth
• Find population after n years; find rate given initial and final population
• Combined growth and decline: A = P(1 + R₁/100)(1 − R₂/100)

Instalment Problems

• Equal periodic payments; ICSE uses 2–3 instalment problems
• Method: equate total amount paid (with interest) to total cash price
• Find instalment amount given cash price, interest rate and number of instalments

ICSE Numericals — Compound Interest

• ₹5000 at 10% p.a. compounded half-yearly for 1.5 years — find CI
• A car depreciates at 15% annually; original cost ₹4,00,000 — value after 3 years
• Find P if A=₹12,100, R=10% p.a., n=2 years