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

How many years will it take for an amount of $Rs. 600$ to yield $Rs. 120$ as interest at $10 \%$ per annum of $S.I.$?

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

Mrs. Sushma lent out an amount of $Rs. 3000$ at $4 \%$ p.a. and some other amount at $5 \%$ p.a. If at the end of the year she received $Rs. 138$ as total interest,what amount (in $Rs.$) did she lend out at $5 \%$ p.a.?

If the simple interest of ₹ $1$ for $1$ month is $1$ paisa,then the rate per cent per annum will be:

$A$ man invests a certain sum of money at $6 \%$ $p.a.$ simple interest and another sum at $7 \%$ $p.a.$ simple interest. His income from interest after $2$ $years$ was $Rs. 354$. One-fourth of the first sum is equal to one-fifth of the second sum. Find the total sum (in $Rs.$) he invested.