$A$ certain sum is invested for a certain time. It amounts to ₹ $450$ at $7 \%$ per annum. But when invested at $5 \%$ per annum,it amounts to ₹ $350$. Find the sum (in ₹).

Nitin borrowed some money at the rate of $6 \% \text{ p.a.}$ for the first three years,$9 \% \text{ p.a.}$ for the next five years,and $13 \% \text{ p.a.}$ for the period beyond eight years. If the total interest paid by him at the end of eleven years is ₹ $8,160$,the money borrowed by him was:

If the annual rate of simple interest increases from $10 \%$ to $12 \frac{1}{2} \%$,a man's yearly income increases by ₹ $1250$. His principal (in ₹) is

When the rate of interest in a bank is reduced from $5 \%$ p.a. to $4.5 \%$ p.a.,Bani deposited $Rs. 4000$ in her savings account. She found that the new interest income remained the same as before. Find her original deposit (in $Rs.$)?

What time (in years) is taken by a sum of $Rs. 7000$ to become $Rs. 10500$ at the rate of $5 \%$ per annum simple interest?

If the difference between the simple interest on a certain sum for $4$ $years$ at $2 \frac{1}{2} \%$ per annum and the simple interest on the same sum for the same period at $3 \%$ per annum is ₹ $60$,then the sum (in ₹) is: