$A$ sum of $Rs. 1500$ amounts to $Rs. 3000$ in five years at a certain rate of simple interest. If the rate of interest is increased by $1 \%$,the same sum in the same time would amount (in $Rs.$) to:

$A$ certain sum doubles in $7$ years at simple interest. The same sum under the same interest rate will become $4$ times in how many years?

What annual instalment (in $Rs.$) will discharge a debt of $Rs. 1092$ due in $3$ years at $12 \%$ simple interest?

The rate of interest for the first $2$ years is $3 \%$ per annum,for the next $3$ years is $8 \%$ per annum,and for the period beyond $5$ years is $10 \%$ per annum. If a man gets $Rs. 1520$ as simple interest for $6$ years,how much money (in $Rs.$) did he deposit?

Bindu lends $Rs. 10000$ in four parts to her friends. If she gets $8 \%$ on $Rs. 2000$,$7.5 \%$ on $Rs. 4000$ and $8.5 \%$ on $Rs. 1400$,what percent must she get for the remainder,if the average interest is $8.13 \%$?

$A$ money lender finds that due to a fall in the annual rate of interest from $8 \%$ to $7 \frac{3}{4} \%,$ his yearly income diminishes by ₹ $61.50$. His capital (in ₹) is: