If at the same rate of interest, in 2 years, the simple interest is ₹40 and compound interest, compounded annually, is ₹41, then what is the principal (in ₹)?​

Correct option is A

Given: 

2 years SI = 40 

2 years CI = 41 

Solution: 

2 years CI - SI = 41 - 40 = 1 

1st years SI = $$\frac{40}2$$ = 20

rate % = $$\frac1{20}$$​  $$\times$$ 100 % = 5%

5% = 20 

Principal 100% 

​$$5\% \times20 = 20 \times20$$ 

100% = 400