Iift 2009 Question 99
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IIFT 2009
Top face will look like the figure shown below.
Curved surface area of the cylinder = 2 ∗ π ∗ r ∗ h
To calculate height of the cylinder in terms of 'r', we can see that traingle ADC is similar to triangle EFC.
Therefore, AD/DC = EF/FC
10/4 = h/4-r
h = 5/2(4-r)
Therefore, the curved surface area of the cylinder = 2 ∗ π ∗ r ∗ 5/2(4 −r) = 5πr(4 − r)
Hence, option B is the correct answer.