In how many years will a sum of money treble itself at $10 \%$ per annum simple interest?

If the amount obtained by Mahesh by investing ₹ $1500$ for $2 \frac{1}{2}$ years at the rate of $8 \%$ $p.a.$ is equal to the amount obtained by Suresh by investing a certain sum for $2$ years at $5 \%$ $p.a.$ simple interest,then the sum invested by Suresh is

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?

Ram deposited a certain sum of money in a company at $12 \%$ per annum simple interest for $4$ years and deposited an equal amount in a fixed deposit in a bank for $5$ years at $15 \%$ per annum simple interest. If the difference in the interest from the two sources is $Rs. 1350$,then the sum (in $Rs.$) deposited in each case is:

$A$ man buys a watch for ₹ $1950$ in cash and sells it for ₹ $2200$ at a credit of $1$ $year$. If the rate of interest is $10 \%$ $p.a.$,what is his profit or loss?

The simple interest on a sum of money is $\frac{1}{9}$ of the principal and the number of years is equal to the rate per cent per annum. The rate per cent per annum is equal to