In how many years will a sum of money become double at $\displaystyle 5\%$ p.a compound interest

$\displaystyle P 8,000/-$ at $\displaystyle 10\%$ p.a. interest compounded half yearly will become at the end of one year

If $\displaystyle P 1,000$ be invested at interest rate of $\displaystyle 5\%$ and the interest be added to the principal every $\displaystyle 10$ years, then the number in years in which it will amount to $\displaystyle P 2,000$ is:

A person borrows $\displaystyle P 5,000$ for $\displaystyle 2$ years at $\displaystyle 4\%$ per annual simple interest. He immediately lends to another person at $\displaystyle 6.25\%$ per annum for $\displaystyle 2$ years find his gain in the transaction for year:

If an amount is kept at S. I. it earns an interest of $\displaystyle P 600$ in first two years but when kept at compound interest it earns an interest of $\displaystyle P 660$ for the same period, then the rate of interest and principal amount respectively are:

If $\displaystyle P 10,000$ is invested at $\displaystyle 8\%$ p.a. compounded quarterly, then the value of the investment after $\displaystyle 2$ years is. (Given $\displaystyle (1.02)^8 = 1.171659)$

A bank pays $\displaystyle 10\%$ rate of interest compounded annually. A sum of $\displaystyle P 400$ is deposited in the bank. The amount at the end of $\displaystyle 1$ year will be