This question was previously asked in

UPSSSC Chakbandi Lekhpal Official Paper 1 (Held on : 30 Sept 2019 Shift 1)

- 27π cm
^{2} - 18π cm
^{2} - 24π cm
^{2} - 21π cm
^{2}

Option 1 : 27π cm^{2}

Given

The volume of a semi - sphere = 18π cm3

**Formula used:**

The volume of the semi-sphere = (2/3)πr^{3}

The total area of the semi-sphere = 3πr2

Calculation

According to the question,

The volume of the semi-sphere = (2/3)πr3

⇒ 18π = (2/3)πr3

⇒ 9 = r^{3}/3

⇒ r^{3} = 27

⇒ r = 3.

Now, The total surface area of the semi-sphere = 3πr2

⇒ 3πr^{2 }

⇒ 3π × 3^{2}

⇒ 27π

** ∴ The total surface area of that semi-sphere is 27π cm ^{2}**

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