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Ex.13.4 Q3 Surface Areas and Volumes Solution - NCERT Maths Class 9

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Question

Find the total surface area of a hemisphere of radius \(10\rm\, cm.\) \((\rm{Use\;\pi = 3.14})\)

 Video Solution
Surface-Areas-And-Volumes
Ex exercise-13-4 | Question 3

Text Solution

Reasoning:

A hemisphere is half of a sphere having one circular surface at the top.

\(∴\)  Total surface area of a hemisphere is the half area of sphere and the top circular \({\rm{area}} = 3\pi {r^2}\)

What is known?

Radius of the hemisphere.

What is unknown?

Total surface area of the hemisphere.

Steps:

Radius of the hemisphere\( (r) = 10 \rm\,cm\)

Total Surface area

\[\begin{align} &= 3\pi {r^2}\\&= 3 \times 3.14 \times 10 \times 10\\&= 942\,\,\rm{cm^2} \end{align}\]

Answer:

Total surface area of the hemisphere \( = 942\,\rm{cm^2} \)