Skip to content
Exercise 7.4 · Q4

Q.To what amount will ₹12000 accumulate in 12 years if invested at an effective rate of 5%?

Sikkim CbseNCERTSubjective· 3mImportance★★★★★
58% · 42/72 Questions
🔒 Locked · start free trial →

You're viewing a preview — the full solution, concept, methods & PYQ mapping are locked.

Start your 14-day free trial to unlock the full solution →

The key idea is that compound interest grows money exponentially, not linearly. Using the formula A=P(1+i)nA = P(1 + i)^n, ₹12000 at 5% effective annual rate for 12 years accumulates to approximately ₹21,550.

Compound interest means that each year, the interest earned is added to the principal, and the next year’s interest is calculated on this larger amount. This is why it’s called “interest on interest.” The effective rate of 5% means that after one year, ₹100 becomes ₹105 — no compounding within the year, just once per year.

The formula is straightforward:

A=P(1+i)nA = P(1 + i)^n

where AA is the accumulated amount, PP is the principal, ii is the effective interest rate per period (as a decimal), and nn is the number of periods.

Here, P=12000P = 12000, i=0.05i = 0.05, and n=12n = 12.

  1. Set up the calculation.

    We need A=12000×(1.05)12A = 12000 \times (1.05)^{12}.

  2. Compute (1.05)12(1.05)^{12}.

    You can do this step by step, but it’s faster to use a calculator or logarithms. Let’s break it down for understanding:

    • (1.05)2=1.1025(1.05)^2 = 1.1025
    • (1.05)4=(1.1025)2=1.21550625(1.05)^4 = (1.1025)^2 = 1.21550625
    • (1.05)8=(1.21550625)2≈1.477455(1.05)^8 = (1.21550625)^2 \approx 1.477455
    • Then (1.05)12=(1.05)8×(1.05)4≈1.477455×1.215506≈1.795856(1.05)^{12} = (1.05)^8 \times (1.05)^4 \approx 1.477455 \times 1.215506 \approx 1.795856

    More precisely, using a calculator: (1.05)12≈1.795856326(1.05)^{12} \approx 1.795856326.

  3. Multiply by the principal.

A=12000×1.795856326≈21550.2759A = 12000 \times 1.795856326 \approx 21550.2759

  1. Round to the nearest rupee. …

Unlock everything free for 14 days

  • Full step-by-step solutions
  • Concept-first explanations
  • Methods, shortcuts & mistakes
  • PYQ mapping + timed mock tests

Full access for 14 days. No credit card required.