A hemispherical and a conical hole is scooped out of a solid wooden cylinder. Find the volume of the remaining solid where the measurements are as follows :

The height of the solid cylinder is 7 cm, radius of each of hemisphere, cone and cylinder is 3 cm. Height of cone is 3 cm. Give your answer correct to the nearest whole number.

A cylinder, a hemisphere and a cone have equal base diameters and have the same height. Prove that their volumes are in the ratio 3 : 2 : 1.

If the radius of a sphere is increased by 50%, find the increase per cent in its volume.

If the ratio of the volume of two spheres is 1 : 8, find the ratio of their surface areas.