$A$ sum of money at simple interest becomes four times in $24$ years. The rate per cent of interest per annum is

$A$ sum of $Rs. 15000$ amounts to an interest of $Rs. 4500$ in $5$ years. What is the rate of interest (in percentage)?

The sum of money that will produce ₹ $1770$ interest in $7 \frac{1}{2}$ years at $8 \%$ simple interest per annum is:

Mr. Thomas invested an amount of $Rs. 13,900$ divided in two different schemes $A$ and $B$ at the simple interest rate of $14 \%$ $p.a.$ and $11 \%$ $p.a.$ respectively. If the total amount of simple interest earned in $2$ $years$ be $Rs. 3508$,what was the amount (in $Rs.$) invested in Scheme $B$?

$₹ 800$ becomes $₹ 956$ in $3$ years at a certain rate of simple interest. If the rate of interest is increased by $4 \%$,what amount (in $₹$) will $₹ 800$ become in $3$ years?

$A$ sum fetched a total simple interest of $Rs. 4016.25$ at the rate of $9 \%$ $p.a.$ in $5$ years. What is the sum (in $Rs.$)?