Alipta received some amount of money from her father. In how many $years$ will the ratio of the money (principal) and the interest obtained from it be $10: 3$ at the rate of $6 \%$ simple interest per annum?

$Rs. 600$ becomes $Rs. 720$ in $4$ $years$ at simple interest. If the rate of interest is increased by $2 \%$,what will be the total amount (in $Rs.$)?

$A$ money lender lends ₹ $400$ for $3$ $years$ to a person and ₹ $500$ for $4$ $years$ to another person at the same rate of simple interest. If altogether he receives ₹ $160$ as interest,what is the rate of interest per annum (in $\%$)?

The population of Mumbai increases by $5 \%$ per annum. Its population was $100000$ in $2004$. What was its population after $3$ years?

David invested a certain amount in three different schemes $A, B$ and $C$ with the rate of interest $10 \% \text{ p.a.}, 12 \% \text{ p.a.}$ and $15 \% \text{ p.a.}$ respectively. If the total interest accrued in one year was ₹ $3200$ and the amount invested in scheme $C$ was $150 \%$ of the amount invested in scheme $A$ and $240 \%$ of the amount invested in scheme $B$, what was the amount (in ₹) invested in scheme $B$?

Ram deposited a certain sum of money in a company at $12 \%$ per annum simple interest for $4$ years and deposited an equal amount in a fixed deposit in a bank for $5$ years at $15 \%$ per annum simple interest. If the difference in the interest from the two sources is $Rs. 1350$,then the sum (in $Rs.$) deposited in each case is: