A deposited Rs. 8,000 in a bank at 8% per annum simple interest. B deposited Rs. 6,000 at 10% compound interest per annum. After 3 years the difference between their interest will be:

Correct option is C

​Given:

A's investment:

Principal(P) = Rs. 8000, Rate(R) = 8%, Time(T) = 3 years (Simple Interest).

 B's investment:

Principal(P) = Rs. 6000, Rate(R) = 10%, Time(T) = 3 years (Compound Interest).

Formula Used:

Simple Interest:

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

Compound Interest:

​$$\text{CI} = P \times \left(1 + \frac{R}{100}\right)^T - P$$​​

Solution:

For A's investment :

$$\text{SI} = \frac{8000 \times 8 \times 3}{100} = Rs. 1920$$​​

For B's investment:

$$\text{CI} = 6000 \times \left(1 + \frac{10}{100}\right)^3 - 6000 \\ \ \\= 6000 \times (1.1)^3 - 6000$$​​

​$$\text{CI} = 6000 \times 1.331 - 6000\\ \ \\ = 7986 - 6000 = Rs. 1986$$​​

Difference of SI and CI:

=  $$1986 - 1920 = Rs. 66$$​​