8. A heap of rice is in the form of a cone of diameter 12 m. and height 8 m. Find its volume?How much canvas cloth is required to cover the heap ? (Use p = 3.14)

9. The curved surface area of a cone is 4070 cm 2 and its diameter is 70 cm. What is its slant height?

We have seen solids which are made up of combination of solids known like sphere cylinder and cone. We can observe in our real life also like wooden things, house items, medicine capsules, bottles, oil-tankers etc., We eat ice-cream in our daily life. Can you tell how many solid figures are there in it? It is usually made up of cone and hemisphere.

Lets take another example, an oil-tanker /water-tanker. Is it a single shaped object? You may guess that it is made up of a cylinder with two hemisphere at it ends.

If, for some reason you want to find the surface areas or volumes or capacities of such objects, how would you do it? We cannot classify these shapes under any of the solids you have already studied.

As we have seen, the oil-tanker was made up of a cylinder with two hemispheres stuck at either end. It will look like the following figure:

If we consider the surface of the newly formed object, we would be able to see only the curved surfaces of the two hemisphere and the curved surface of the cylinder.

TSA of new solid = CSA of one hemisphere + CSA of cylinder + CSA of other hemisphere

Here TSA and CSA stand for ‘total surface area’ and ‘curved surface area’ respectively. Now let us look at another example.

Devarsha wants to make a toy by putting together a hemisphere and a cone. Let us see the steps that he should be going through.