$A$ sum invested at $5 \%$ simple interest per annum grows to ₹ $504$ in $4$ years. The same amount at $10 \%$ simple interest per annum in $2 \frac{1}{2}$ years will grow to (in ₹):

At what percent of simple interest will a sum of money double itself in $15$ years?

At what rate per cent per annum will a sum of money double in $16$ years (in $.25$)?

If the difference between the simple interest on a certain sum for $4$ $years$ at $2 \frac{1}{2} \%$ per annum and the simple interest on the same sum for the same period at $3 \%$ per annum is ₹ $60$,then the sum (in ₹) is:

Simple interest on a certain sum is $\frac{16}{25}$ of the sum. If the rate per cent and time (in years) are equal,then the rate per cent is:

The rate percent per annum at which ₹ $1200$ amounts to ₹ $1440$ in $4$ years is: