Which of the following books is written by Dadabhai

Find the number of common tangents, if r1 + r2 = C1C2 .(With usual notations, r1 & r2 and C1 & C2 are the radii and centres of the two circles.)

Mr. Arun rows a boat with the stream at 10 km/hr and against the stream in 5 km/hr. In still water, his rate of rowing in km/h is:

The volume of a cube is 1000 cm³. If the cost of painting the cube is Rs. 8 per cm², then find the cost of painting five faces of the cube.

The volume of water measured on a rectangular field 400m `xx` 200m is 8000 . Find the depth (amount) of rain that has fallen.

The volume of a cone is 128π cubic centimeters. If the radius of the base is 4 cm, find the height of the cone.

At the end of a business conference the ten people present all shake hands with each other once. How many handshakes will there be altogether?

The length of the rectangle is triple its breadth. If the perimeter of the rectangle is 56 m, then find the area (in m²) of the rectangle.