Mehak lent $₹8,000$to Ria at the rate of $12\frac{1}{2}\%$ per annum compound interest. Kind the amount payable by Ria to Mehak after $2$ years.

Sanjay borrowed $₹12,800$ at the rate of $6 \frac{1}{4}\%$per annum at simple interest. On the same day. he lent it to Rajesh at the same rate but compounded annually. What does Sanjay gain at the end of $2$ years?

In how many years will $₹4,000$ amount to$₹5,324$ at the rate of $10\%$ per annum compounded annually?