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Find the total surface area of a cylinder whose radius is 7 cm and height is 10 cm. (Use pi = 22/7)
748┬аcm2
648┬аcm2
848┬аcm2
548┬аcm2
748┬аcm2
Since the radius is 7, the area formula 2imes(22/7)imes7imes(7+10) simplifies to 44imes17. Multiplying 44imes17 is easy: 44imes10=440 and 44imes7=308; 440+308=748.
Radius r = 7 cm, height h = 10 cm, pi = 22/7
TSA=2╧Аr(r+h)
Since the radius is 7, the area formula 2imes(22/7)imes7imes(7+10) simplifies to 44imes17. Multiplying 44imes17 is easy: 44imes10=440 and 44imes7=308; 440+308=748.
Students often use the formula for Lateral Surface Area (2╧Аrh) instead of Total Surface Area (2╧Аr(r+h)), ignoring the two circular bases.
Identify parameters
We are given the radius r=7 cm and the height h=10 cm of the cylinder.
r=7,h=10
Apply Total Surface Area formula
The formula for the total surface area of a cylinder is the sum of its lateral surface area and the areas of the two circular bases.
TSA=2╧Аr(r+h)
Substitute and Solve
Substituting r=7, h=10, and ╧А=22/7: TSA=2imes(22/7)imes7imes(7+10)=44imes17.
TSA=44imes17=748┬аcm2
A is correct because the calculated total surface area is 748 cm┬▓.
This concept is foundational for understanding volume of composite solids where you may need to subtract shared surfaces (e.g., when a cylinder is joined to a hemisphere).