If the radius of a cylinder is doubled and its height remains unchanged, then its curved surface area is increased by times. A) 2
If the radius of a cylinder is doubled and its height remains unchanged, then its curved surface area is increased by times.
A) 2
B) 3
C) half
D) unchange
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Correct option is: A) 2
Let the original radius be r and height be h.
\(\therefore\) Curved surface area of original cylinder = \(2 \pi rh\)
When the radius is doubled with height remaining unchanged, the new curved surface area will be
= \(2 \pi (2r) h = \) \(4 \pi rh\) = 2 (\(2 \pi rh\))
= 2 (Curved surface area of original cylinder)
Hence, its curved surface area is increased by 2 times.
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