Multiple choice

A sum invested at a certain rate of interest per annum, compounded annually, amounts to ₹3,600 in 2 years and to ₹6,480 in 4 years. What is the sum invested?

  1. ₹2,500

  2. ₹2,000

  3. ₹2,400

  4. ₹23600

Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let principal = P and rate = r%. Amount after 2 years: P(1 + r/100)² = 3600. After 4 years: P(1 + r/100)⁴ = 6480. Dividing: (1 + r/100)² = 6480/3600 = 1.8. So P × 1.8 = 3600, giving P = ₹2000. Option D (₹23600) appears to be a typo for ₹2,360, which is incorrect. The compound interest doubles between years 2 and 4, confirming the calculation.