What is the compound interest accrued on an amount of Rs 12000 at the rate of 9 p.c.p.a at the end of 2 years?

Interest earned on an amount after $2$ years at $20\%$ P.A. compounded yearly is $₹1716.$ Find the interest earned on same amount after $3$ years at $15\%$ P.A. at simple interest?

What will be the compound interest on a sum of Rs. 160000 for 2 years at the annual rate of 10%, if the interest is compounded half yearly?

Two different amounts are invested in two schemes. In scheme A, amount $X$ is invested at $8\%$ per annum and in scheme B amount $(X+1400)$ is invested at $12\%$ per annum. After $2$ years difference between both interests is $880$, then find value of $X$.

A sum of $₹ 2500$ becomes $₹ 8100$ in $2$ years at a certain rate of compound interest. What will be the sum (in $₹$) after $4$ years?