What sum lent at $10 \%$ per year on $S.I.$ will amount to $Rs. 450$ in $2$ years?

$A$ 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.

$A$ 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:

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?

Girish invested some money in a bank. After $8$ years,his amount became triple. How many times of the original sum will the money become in $20$ years at simple interest?

If the simple interest on a certain sum of money for $2$ $years$ is one-fifth of the sum,then the rate of interest (in $\%$) per annum is