Gaurav borrowed $Rs. 800$ at $6 \%$ and Naresh borrowed $Rs. 600$ at $10 \%$. After how much time will they both have equal debts?

Peter invested an amount of ₹ $12,000$ at the rate of $10 \%$ $p.a.$ simple interest and another amount at the rate of $20 \%$ $p.a.$ simple interest. The total interest earned at the end of one year on the total amount invested became $14 \%$ $p.a.$ Find the total amount (in ₹) invested.

Sumit lent some money to Mohit at $5 \%$ $p.a.$ simple interest. Mohit lent the entire amount to Birju on the same day at $8 \frac{1}{2} \%$ $p.a.$ In this transaction,after a year Mohit earned a profit of ₹ $350.$ Find out the sum of money (in ₹) lent by Sumit to Mohit.

$A$ part of $Rs. 38800$ is lent out at $72 \%$ per annum for six months. The rest of the amount is lent out at $5 \%$ per annum after one year. The ratio of interest after $3$ years from the time when the first amount was lent out is $5: 4$. Find the second part that was lent out at $5 \%$ (in $Rs.$).

$A$ sum of ₹ $8000$ is divided into two parts. The simple interest on the first part at the rate of $21 \%$ per annum is equal to the simple interest on the second part at the rate of $35 \%$ per annum. What is the interest (in ₹) of each part?

$A$ certain amount earns simple interest of ₹ $1,750$ after $7$ years. Had the interest rate been $2 \%$ more per annum,how much more interest would it have earned (in ₹)?