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

The simple interest on a certain sum of money at the rate of $5 \%$ per annum for $8$ years is ₹ $840$. What is the rate of interest per annum for which the same amount of interest can be received on the same sum after $5$ years (in $\%$)?

An amount fetched a total simple interest of ₹ $3200$ at the rate of $6.25 \%$ per year in $4$ years. What is the amount (principal) in ₹?

What annual payment (in $Rs.$) will discharge a debt of $Rs. 770$ due in $5$ years,the rate of interest being $5 \%$ per annum?

$A$ 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:

The simple interest on a sum of money will be ₹ $600$ after $10$ $years$. If the principal is trebled after $5$ $years$,then what will be the total interest (in ₹) at the end of the tenth year?