A sum of money doubles itself in 4 years at compound interest. It will amount to 8 times of itself at the same rate of interest in-

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?

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 $X$.

What is the ratio of simple interest earned on certain amount at the rate of $12\%$ p.a. for $9$ years and that for $12$ years ? 

1. $1:2$
2. $2:3$
3. $3:4$
4.$4:5$

On a certain principal, simple interest amounts to Rs. 1000 in 1 year at the rate of 10% p.a. What will be the effective rate of interest if the same is compounded on a half-yearly basis?

1. 10.10
2. 10.15
3. 10.20
4. 10.25