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# The total surface area of a cone whose radius is r/2 and slant height 2l is

a. 2πr (l + r)

b. πr (l + r/4)

c. πr (l + r)

d. 2πrl

**Solution:**

Given, the radius of the cone is r/2

Slant height is 2l

We have to find the total surface area of the cone.

Total surface area of the cone = πr(l + r)

Where, r is the radius of the cone

l is the slant height

Given, r = r/2

l = 2l

Total surface area = π(r/2)(2l + r/2)

= π[(r/2)(2l) + (r/2)(r/2)]

= π[rl + r²/4]

= πr(l + r/4)

Therefore, the total surface area is πr(l + r/4)

**✦ Try This: **The total surface area of a cone whose slant height is 2l is

Given, the Slant height of the cone is 2l

We have to find the total surface area of the cone.

Total surface area of the cone = πr(l + r)

Where, r is the radius of the cone

l is the slant height

Given, l = 2l

Total surface area = πr(2l + r)

Therefore, the total surface area is πr(2l + r)

**☛ Also Check: **NCERT Solutions for Class 9 Maths Chapter 13

**NCERT Exemplar Class 9 Maths Exercise 13.1 Problem 5**

## The total surface area of a cone whose radius is r/2 and slant height 2l is a. 2πr (l + r), b. πr (l + r/4), c. πr (l + r), d. 2πrl

**Summary:**

The total surface area of a cone whose radius is r/2 and slant height 2l is πr(l + r/4)

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