If the side of the square is increased by 30%, then how much % does its area get increased?

If 3 ^(X-Y)=27 and 3 ^(X+Y)=243, then X is equal to:

A pilot in an aeroplane at an altitude of 200 m observes two points lying on either side of a river. If the angles of depression of the two points be 45 ° and 60 °, then the width of the river is 

If $$ {cot A={n\over{n+1}}}$$ and $$ {cot B={1\over{2n+1}}}$$ then what is the value of cot (A + B)?

A certain sum of money at a certain rate doubles itself in 9 years, then in how many years it will become the same sum will be 5 times of itself?

By selling an article for Rs. 450, I lose 20%. For what price should I sell it to gain 20% ? 

Point P is the midpoint of segment AB. Co-ordinates of point Pare (2,1) and point B are (11,5) Co-ordinates of point A are 

The average marks of a student in an examination is 63, if he had scored 20 marks in geography and 2 more marks in history, his average marks would have been 65. How many subjects were there in the exam?