CBSE Class 10-Mathematics: Chapter –13 Surface Areas and Volumes Part 20

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Question 17:

The radius of the base and the height of solid right cylinder are in the ratio and its volume is . Find the total surface area of the cylinder.


Let r be the radius of the base and h be the height of the solid right circular cylinder.

Volume of the cylinder

Surface area of cylinder

Question 18:

A toy is in form of a cone mounted on a hemisphere of common base radius 7 cm. The total height of the toy is , find the total surface area of the toy.


Total surface area of . of hemisphere . of cone


T.S.A. of

Question 19:

A well in diameter and deep be dug in rectangular field by . The earth taken out is spread evenly on the field. Find the level of the earth raised in the field.


Radius of well

Depth of well

Volume of earth taken out

Area of field excluding well

Level of earth raised

Question 20:

A solid sphere of radius is melted into a hollow cylinder of uniform thickness. If the external radius of the base of cylinder is and its height is , find the uniform thickness of the cylinder.


Volume of sphere

Let the internal radius of cylinder

External radius


Volume of the hollow cylinder Volume of sphere