An Aeroplan is flying horizontally at a height of 1.8 km above the ground. The angle of elevation of plane from point X is 60° and after 20 seconds, its angle of elevation from X becomes 30°, If point X is on ground, then what is the speed (in km / hr.) of Aeroplan? 

If $$ {x+{1\over x}=\sqrt{3}}$$ then $$ {x^{48}+x^{378\over7}+x^{726\over11}+x^{60}}$$ is equal to

An iron pipe 20 cm long has exterior diameter 25 cm. If the thickness of the pipe is 1 cm, then the whole surface area of the pipe?

Mohan bought 25 books for Rs. 2,000 and sold them at a profit equal to the selling price of 5 books. The selling price of 1 book is: 

A man borrows some money at 3% simple interest per annum and lends it to somebody at 5% interest to be compounded annually. By this he makes a profit of Rs.541 at the end of 3 years. The money he borrowed was-

The angle of elevation of the top of two vertical towers as seen from the middle point of the line joining the foot of the towers are 60° and 30°, respectively. The ratio of the heights of the tower is

0.8% of a number is 31, then find the number.

While solving a problem, by mistake, Anita squared a number and then subtracted 25 from it rather than first subtracting 25 from the number and then squaring it. But she got the right answer. What was the given number?