$A$ sum of money becomes $\frac{8}{5}$ of itself in $5$ $years$ at a certain rate of interest. The rate per cent 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:

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 $B$?

The simple interest on a sum for $8$ years is ₹ $47500$. The rate of interest is $10 \%$ per annum for the first $5$ years and $15 \%$ per annum for the next $3$ years. What is the value (in ₹) of the sum?

In how many years will ₹ $150$ produce the same interest at $8 \%$ per annum as ₹ $800$ produces in $3$ years at $4 \frac{1}{2} \%$ per annum?

What time (in years) is taken by a sum of $Rs. 7000$ to become $Rs. 10500$ at the rate of $5 \%$ per annum simple interest?