The annual instalment that will discharge a debt of ₹ $4200$ due in $5$ years at $10 \%$ simple interest (in ₹) is:

$A$ sum was doubled with $12 \frac{1}{2} \%$ rate of simple interest per annum. The time taken (in years) for that sum is:

₹ $800$ becomes ₹ $956$ in $3$ $years$ at a certain rate of simple interest. If the rate of interest is increased by $4 \%,$ what amount (in ₹) will ₹ $800$ become in $3$ $years?$

What is the $S.I.$ on $Rs. 800$ at $5 \%$ per annum for $3$ years?

At what percent of simple interest will a sum of money double itself in $15$ years?

Arun lends ₹ $20,000$ to two of his friends. He gives ₹ $12,000$ to the first at $8 \%$ p.a. simple interest. Arun wants to make a profit of $10 \%$ on the whole. The simple interest rate $\%$ at which he should lend the remaining sum of money to the second friend is