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Find the total surface area of a cylinder whose radius of base is 7┬аcm and height is 12┬аcm.
303╧А┬аcm2
266╧А┬аcm2
208╧А┬аcm2
280╧А┬аcm2
266╧А┬аcm2
Use the formula for total surface area directly and note that ╧А├Ч7=22, which helps simplify calculations involving multiples of 7.
Radius of base of cylinder r=7┬аcm, height of cylinder h=12┬аcm
A=2╧Аr(r+h)
Use the formula for total surface area directly and note that ╧А├Ч7=22, which helps simplify calculations involving multiples of 7.
Confusing the total surface area formula with the curved surface area formula (2╧Аrh) by forgetting to add the area of the two circular bases (2╧Аr2).
Identify Given Parameters
The radius of the base of the cylinder is given as r=7┬аcm and the height is h=12┬аcm.
r=7┬аcm,h=12┬аcm
Recall Total Surface Area Formula
The total surface area (A) of a solid cylinder includes the curved surface area and the areas of the two circular bases: A=2╧Аrh+2╧Аr2=2╧Аr(r+h).
A=2╧Аr(r+h)
Substitute Values into the Formula
Substitute r=7 and h=12 into the formula: A=2├Ч╧А├Ч7├Ч(7+12).
A=2├Ч╧А├Ч7├Ч(19)
Calculate the Final Area
Multiply the numbers: 2├Ч7=14, and 14├Ч19=266. Therefore, the total surface area is 266╧А┬аcm2.
A=266╧А┬аcm2
B is correct because substituting r=7┬аcm and h=12┬аcm into the total surface area formula 2╧Аr(r+h) yields 2├Ч╧А├Ч7├Ч(7+12)=266╧А┬аcm2.
Always verify whether the question asks for Curved Surface Area (CSA) or Total Surface Area (TSA), as CSA excludes the top and bottom circular bases.