If the simple interest on a certain sum of money is ₹ $256$ and the rate of interest per annum equals the number of years,then the rate of interest (in $\%$) is:

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

The population of a particular area of a city is $5000$. It increases by $10 \%$ in $1^{st} \,yr$. It decreases by $20 \%$ in the $2^{nd} \,yr$ because of some reason. In the $3^{rd} \,yr$ the population increases by $30 \%$. What will be the population of the area at the end of $3$ $years$?

Brinda borrowed ₹ $1000$ to build a hut. She pays $5 \%$ simple interest. She lets the hut to Ramu and receives a rent of ₹ $12 \frac{1}{2}$ per month from Ramu. In how many years would Brinda clear off the debt?

The principal (in ₹) that will yield ₹ $60$ as simple interest at $6 \%$ per annum in $5$ years is

The annual instalment that will discharge a debt of ₹ $4200$ due in $5$ years at $10 \%$ simple interest (in ₹) is: