What will be the compound interest (compounded annually) of 3 years at the rate of 12.5 percent on an amount of Rs. 5120?

If 5^√x + 12^√x = 13^√x, then x is equal to: 

A trader allows a trade of 20% and a cash discount of $$6{1\over 4}\%$$% on the marked price of the goods and gets a net gain of 20% of the cost. By how much above the cost should the goods be marked for the sale? 

simplify the following equation
$$ (1-{1\over3})(1-{1\over4})(1-{1\over5})......(1-{1\over n})$$

Which amount will be Rs 520 in 5 years with simple interest and Rs 568 in 7 years?

A and B leave from point M at the same time towards point N. B reaches N and starts towards M instantly. He meets A at point O (between M and N). The distance between M and N is 245 km. If the speeds of A and B are 26 km/h and 65 km/h, respectively, then what is the distance between O and N?

A sum of ₹ 10,000 is lent partly at 8 % and remaining at 10% per annum. If the yearly interest on the average is 9.2 %, the two parts are 

A merchant loses 10% by selling an article. If the cost price of the article is ₹ 15, then the selling price of the article is