Direction: A hollow cylindrical tank whose bottom is closed and top is open is painted from outside as well as inside. The inner radius of the cylinder is 7 cm, and its thickness is 2 cm. The height of the cylinder is 21 cm.

If another identical cylinder is placed over it, such that both the cylinders overlap each other, and their open ends combine together to form a new solid cylinder. Find the total surface area (in $s q c m$ ) of the new cylinder.

788 π

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918 π

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755 π

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808 π

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Solution

The correct option is B $918 π$
The height of the new structure formed $= 21 + 21 = 42 c m$
Its radius $= 9 c m$
So, TSA of the structure $= 2 π r (r + h) = 2 \times π 9 (9 + 42) = 918 π S q c m$
Hence, option $D$ is the correct answer.

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Direction: A hollow cylindrical tank whose bottom is closed and top is open is painted from outside as well as inside. The inner radius of the cylinder is 7 cm, and its thickness is 2 cm. The height of the cylinder is 21 cm.

Using the data given in the previous question, find the difference (in

s q c m

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4620

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115.5

sq. cm. and height

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cm. Find the thickness of the cylinder.

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The correct option is B 918πThe height of the new structure formed =21+21=42 cm Its radius =9 cm So, TSA of the structure =2π r(r+h)=2× π 9(9+42)=918π Sq cm Hence, option D is the correct answer.

The correct option is B $918 π$
The height of the new structure formed $= 21 + 21 = 42 c m$
Its radius $= 9 c m$
So, TSA of the structure $= 2 π r (r + h) = 2 \times π 9 (9 + 42) = 918 π S q c m$
Hence, option $D$ is the correct answer.