If the interest on ₹ $12000$ is more than the interest on ₹ $10000$ by ₹ $500$ in $3$ $years$,the rate percent per annum is:

$A$ 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:

The population of a town is $11200$. It increases by $25\%$ in the first year and decreases by $15\%$ in the second year. What is the population of the town at the end of $2$ years?

David invested a certain amount in three different schemes $A, B$ and $C$ with the rate of interest $10 \% \text{ p.a.}, 12 \% \text{ p.a.}$ and $15 \% \text{ p.a.}$ respectively. If the total interest accrued in one year was ₹ $3200$ and the amount invested in scheme $C$ was $150 \%$ of the amount invested in scheme $A$ and $240 \%$ of the amount invested in scheme $B$, what was the amount (in ₹) invested in scheme $B$?

Arun invested a sum of money at a certain rate of simple interest for a period of $4$ years. Had he invested the same sum for a period of $6$ years,the total interest earned by him would have been $50\%$ more than the earlier interest amount. What was the rate of interest per cent per annum?

Mr. Irani borrowed a sum of ₹ $10000$ from a finance company for $6$ years at $8 \%$ per annum. The amount (in ₹) returned by Mr. Irani to the finance company is: