A sum, when invested at 10% simple interest per annum, amounts to Rs. 2640 after 2
years. What is the simple interest (in Rs.) on the same sum at the same rate of interest in 2 years?

Correct option is B

Given:

Amount (A) = Rs. 2640
Rate of interest (R) = 10% per annum
Time (T) = 2 years

Formula Used:

Amount (A) = Principal (P) + Simple Interest (SI)
A = P + (P × R × T) / 100

Solution:

We are given the total amount after 2 years is Rs. 2640. Let the principal be P.
2. According to the formula for amount:
​$$A = P + \frac{P \times R \times T}{100} \\\ \\2640 = P + \frac{P \times 10 \times 2}{100} \\\ \\2640 = P + \frac{20P}{100} \\\ \\2640 = P + \frac{P}{5} \\\ \\2640 = \frac{5P + P}{5} \\\ \\2640 = \frac{6P}{5} \\\ \\2640 \times 5 = 6P \\\ \\13200 = 6P$$​​
P = 13200 / 6 = 2200
Now, to find the Simple Interest (SI):
​$$SI = \frac{(P × R × T) }{100} =\frac{ (2200 × 10 × 2) }{ 100} \\\ \\SI = \frac{44000 }{100} = 440$$​​
Thus, the Simple Interest is Rs. 440.