A sum amounts to ₹ 9680 in 2 years and to ₹ 10648 in

Home » Aptitude » Compound Interest » Question

A sum amounts to ₹ 9680 in 2 years and to ₹ 10648 in 3 years compounded annually. Find the principal and the rate of interest per annum.

1. 12% ; ₹ 7500
2. 10% ; ₹ 8000
3. 11% : ₹ 11000
4. None of these

Correct Option: B

Let Principal = P , Rate = r% p.a.
Here , A₁ = ₹ 9680 , t₁ = 2 years , A₂ = ₹ 10648 , t₂ = 3 years
Interest on ₹ 9680 for 1 year = 10648 – 9680 = ₹ 968

∴ r =	968 × 100	= 10%
	9680

Using the given formula,

A = P		1 +	r		^t
			100

we get ,

9680 = P		1 +	10		²	= P		11		²
			100					10

⇒ P = 9680 ×	10	×	10	= 8000
	11		11

∴ Principal = ₹ 8000.