Mensuration Test

Result

Mensuration Test - 7

Score
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Rank
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TIME Taken - -

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Weekly Quiz Competition

Question 1
1 / -0

If the radius of a sphere is 3k, its surface area is _____.

A
9π k²

B
36π k²

C
18π k²

D
27π k²

Solution

Given, radius (r) of sphere = 3k
Surface area of sphere = 4πr²
= 4π (3k)²
= 4π (9k²)
= 36πk²
Question 2
1 / -0

A sphere with radius r is cut into two halves by a plane passing through the centre of the sphere. Two hemispheres of same radii are formed. Which of the following relations is true in this case?

A
Surface area of the sphere = Sum of the surface areas of the two hemispheres

B
Surface area of the sphere = Sum of the curved surface areas of the two hemispheres

C
Surface area of each hemisphere = Surface area of the sphere

D
Surface area of the sphere = Sum of the total surface areas of the two hemispheres

Solution

Surface area of sphere = 4πr²
And curved surface area of hemisphere = 2πr²

A sphere is cut into two hemispheres.

So, surface area of sphere = C.S.A of the I^st hemisphere + C.S.A of the
II^nd hemisphere

4πr² = 2πr² + 2πr²
4πr² = 4πr²

L.H.S = R.H.S