The angle of elevation of the top of a tower from a point A on the ground is 30^o. On moving a distance of 20 m towards the foot of the tower to a point B, the angle of elevation increase to 60^o.The height of the tower is-

The slant height of a right circular cone is 15 m and its height is 9 m. The area of its curved surface, is:

X, Y and Z take 18 days to complete a piece of work. If X works alone he finishes the work in 36 days and if Y works alone he finishes it in 60 days. How long will it take Z to complete the work alone?

The ratio of two numbers is 2: 3 and their L.C.M is 48.  What is the number?

According to an instruction a mixture of colour and Turpentine containing half part of each is perfect for painting a wall. A painter is provided a mixture, 3 parts of which are colour and 5 parts are Turpentine. How much of the mixture drawn off and replaced with colour so that the mixture becomes perfect?

A sum of money becomes 3 times in 12 years. In how many years it will become 5 times at the same rate of simple interest?

For what value of 'm ' the points A ( m + 1 , 1 ) , B ( 2m + 1,3 ) and C ( 2m + 2 , 2m ) are collinear . 

A crosses a rectangular field at a speed of 52 m / min along its diagonal in 15 seconds and B crosses the ground at the same time by walking at a speed of 68 m / min along its arms. The area of the field is