In what time will ₹ $8100$ produce the same income at $3 \%$ as ₹ $225$ in $4$ years at $3 \%$?

What is the simple interest (in ₹) on ₹ $5400$ in $5$ years at the rate of $12 \%$ per annum?

Asmita invests an amount of $Rs. 9535$ at the rate of $4\%$ per annum to obtain a total amount of $Rs. 11442$ on simple interest after a certain period. For how many years did she invest the amount to obtain the total sum?

What will be the ratio of simple interest earned by a certain amount at the same rate of interest for $6$ years and that of $9$ years?

Arun gives his wife Asha a birthday gift,giving her each year a number of rupees equal to the number of years of her age. If her birthday falls on $August \, 8$,what sum must be placed at simple interest at $7 \%$ on $January \, 1$,before she is $42$,in order to raise the required sum (in $Rs.$)?

If a certain sum of money borrowed at $5 \%$ per annum simple interest amounts to ₹ $1020$ in $4$ years,then the sum of money (in ₹) borrowed is: