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.

Answer:

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.

Answer:

Total surface area of . of hemisphere . of cone

Here,

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.

Answer:

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.

Answer:

Volume of sphere

Let the internal radius of cylinder

External radius

Volume

Volume of the hollow cylinder Volume of sphere