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RS Aggarwal Solutions Class 9 Mathematics Solutions for Volume And Surface Area Of Solids Exercise 15C in Chapter 15 - Volume And Surface Area Of Solids

Question 4 Volume And Surface Area Of Solids Exercise 15C

The curved surface area of a cone is 308cm2 and its slant height is 14cm. Find the radius of the base and total surface area of the cone.

Answer:

ANSWER:

Consider r as the radius of the cone

It is given that

Slant height of the cone = 14cm

The curved surface area of the cone = 308cm2

It can be written as

Πrl = 308

By substituting the values

(22/7) × r × 14 = 308

On further calculation

22 × r × 2 = 308

So we get

r = 308/ (22 × 2)

r = 7cm

We know that

Total surface area of a cone = Πr (l + r)

By substituting the values

The total surface area of a cone = (22/7) × 7 × (14 + 7)

On further calculation

The total surface area of a cone = 22 ×21 = 462 cm2

Therefore, the base radius of the cone is 7cm and the total surface area is 462 cm2.

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