Q. Height of a right circular cylinder is twice it's radius. If the height would be 6 times of it's radius, then volume of the cylinder would be greater by 539 cubic decimeter. Then calculate the height of the cylinder.

Q. Two cubes, whose length of edges are equal, are combined side by side to form a rectangular parallelepiped. If the area of whole surface of the rectangular parallelepiped is 360 sq. cm, then find the volume of each cube.
Q. Prove that the angle in a semicircle is a right angle.
Q. Prove that the opposite angles of a cylic quadrilateral are supplementary.