A sum, when invested at 20% simple interest per annum, amounts to ₹3120 after 3 years. What is the simple interest (in ₹)on the same sum at the same rate in 1 year?

Correct option is C

​Given:

Amount after 3 years = ₹3120

Rate of simple interest = 20% per annum

Time = 3 years

Formula Used:

Amount (A) = Principal (P) + Simple Interest (SI)

SI = $$\frac{P \times R \times T}{100}$$​​

Solution:

Let the principal be P.

SI = $$\frac{P \times 20 \times 3}{100}$$​ = 0.6P

A = P + SI

3120 = P + 0.6P

3120 = 1.6P

P = $$\frac{3120 }{ 1.6 }$$​= ₹1950

Simple interest for 1 year at the same rate:

SI =$$\frac{1950 \times 20 \times 1}{100}$$​​

SI = ₹390

Option (c) is right.