NCERT Class 9 Solutions: Surface Areas and Volumes (Chapter 13) Exercise 13.3 – Part 1

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Q-1 Diameter of the base of a cone is and its slant height is . Find its curved surface area.Solution:

Cone has a slant height s which is given as (because of Pythagoras theorem).

Here, cone radius (r) and slant height (l) . Therefore, curved surface area of the cone

• =

• =

• =

Q-2 Find the total surface area of a cone, if its slant height is and diameter of its base is .Solution:

• Slant height (l)

Total surface area of the cone

Q-3 Curved surface area of a cone is and its slant height is. Find

1. Radius of the base and

2. Total surface area of the cone.

Solution:

Solution (I)

Curved surface of a cone and slant height (l)

Therefore,

Solution (II)

Therefore, total surface area of the cone