A rectangular sheet of dimensions 25 cm into 7 cm is rotated about its longest side
Answers
Answer:
Step-by-step explanation:
Rectangular sheet dimensions = 25 cm X 7 cm.
It is rotated about the edge 25cm. So it forms a 3-d solid. It is a solid cylinder of length (height) h = 25 cm and radius r = 7 cm.
curved surface area CSA
= 2 pi r h
= 2 × 22/7 × 7 × 25 cm^2
= 1, 100 cm^2.
Surface area of two flat sides
= 2 pi r^2
= 2 × 22/7 × 7^2 cm^2
= 308 cm^2
TSA total surface area
= 1,100+308 = 1,408 cm^2
we can also use formula 2 pi r (r+h).
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If we roll the given sheet into a hollow cylinder, then the surface area will be equal to:
If rolling is done along the side of 7 cm:
circumference of hollow cylinder = 7 cm
radius of hollow cylinder = 7 /2π = 49/44 cm
surface area = 2 π r h
= 2 * 22/7 * 49/44 * 25 cm²
If rolling is done along the side of 25 cm
circumference = 25 cm
radius = 25/2π cm =175/44 cm
surface area = 2 π r h = 2 * 22/7 * 175/44 * 7 cm²
Answer:
Step-by-step explanation CM:
Length = 25 CM
Breath = 7 Cm
Parameter = 2×(l+b)
= 2×(25+7)
= 2×32
= 64Cm