Practicing Success

Target Exam

CUET

Subject

General Test

Chapter

Quantitative Reasoning

Topic

Mensuration: 3D

Question:

A hemisphere has 42 cm diameter. Find its curved surface area and the total surface area.

Options:

$2772cm^2 , 4158cm^2$

$3772cm^2 , 5158cm^2$

$4770cm^2 , 4238cm^2$

$3072cm^2 , 4058cm^2$

Correct Answer:

$2772cm^2 , 4158cm^2$

Explanation:

We know that,

Curved surface area = 2πr2

The total surface area = 3πr2

Diameter of the hemisphere = 42 cm

Radius of hemisphere = \(\frac{42}{2}\) = 21 cm

CSA = 2π(21)

= CSA = 2(\(\frac{22}{7}\))(441) 

= CSA = \(\frac{19404}{7}\) = 2772 cm2 

Now , TSA = 3π(21)2 

= TSA = 3(\(\frac{22}{7}\))(441) = \(\frac{29106}{7}\) = 4158 cm2