Question

What is the total surface area of a cone of radius 7cm and height 24cm? (Take π = \(\frac{22}{7}\))

(a) 710 cm^2

(b) 704 cm^2

(c) 700 cm^2

(d) 725 cm^2

This question was addressed to me at a job interview.

Enquiry is from Surface Area of a Right Circular Cone topic in portion Surface Areas and Volumes of Mathematics – Class 9

Answer 1

Right option is (b) 704 cm^2

The best I can explain: Given, r = 7cm and h = 24cm

From the figure,

We can say that according to the Pythagoras theorem, l^2 = r^2 + h^2

= 7^2 + 24^2

= 625

Therefore, l = 25cm

We know that total surface area of a cone = πrl + πr^2

= πr (l + r)

= \(\frac{22}{7}\) * 7 (25+7)

= 704 cm^2.