A sum, when invested at 10% simple interest per annum, amounts to ₹3840 after 2years. What is the simple interest (in ₹) on the same sum at the same rate of interest in2 years?

Correct option is A

Given:

Final amount = ₹3840

Rate of simple interest = 10% per annum

Time = 2 years

Formula Used:

Amount = Principal + Simple Interest

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

Solution:

Let the principal be P

P + SI = 3840

Now, apply the SI formula:

SI = $$\frac{P \times 10 \times 2}{100}$$​​

​$$= \frac{20P}{100}$$​​

​$$= \frac{P}{5}$$​​

So,

​$$P + \frac{P}{5} = 384$$​​

​$$\frac{6P}{5} = 3840$$​​

​$$P = \frac{3840 \times 5}{6} = 3200$$​​

Now, 

SI = 3840 - 3200 = ₹640