$A$ sum of money will double itself in $16$ years at simple interest at an yearly rate of (in $\%$):

$A$ sum of money lent out at simple interest amounts to $Rs. 720$ after $2$ years and $Rs. 1020$ after a further period of $5$ years. Find the principal (in $Rs.$).

Suhit borrowed a sum of $Rs. 6300$ from Vikas at the rate of $14 \%$ per annum for $3$ years. He then added some more money to the borrowed sum and lent it to Mohit at the rate of $16 \%$ simple interest for the same time. If Suhit gained $Rs. 618$ in the whole transaction,what sum did he lend (in $Rs.$) to Mohit?

Hemant makes a fixed deposit of $Rs. 20000$ in Bank of India for a period of $3 \,yr$. If the rate of interest is $13 \%$ $SI$ per annum charged half-yearly,what amount (in $Rs.$) will he get after $42 \,months$?

$A$ sum was doubled with $12 \frac{1}{2} \%$ rate of simple interest per annum. The time taken (in years) for that sum is:

$A$ man invested $\frac{1}{3}$ of his capital at $7 \%$,$\frac{1}{4}$ at $8 \%$,and the remainder at $10 \%$. If the annual income is ₹ $561$,the capital (in ₹) is: