the total surface area of cylinder is 3394 2÷7cm .its height is 21 cm find curved surface area of cylinder
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Solution:-
Given : TSA = 3394 2/7 sq cm or 23760/7 cm and Height = 21 cm
Total surface area of the cylinder = 2πr(r + h)
23760/7 = 2*22/7*r(r + 21)
23760 = 44r(r + 21)
23760 = 44r² + 924r
44r² + 924r - 23760 = 0
Dividing it by 44, we get
r² + 21 - 540 = 0
r² + 36r - 15r - 540 = 0
r(r + 36) - 15(r + 36) = 0
(r + 36) (r - 15) = 0
r = 15 or r = - 36
As radius cannot be negative, so radius = 15 cm.
Curved surface area of the cylinder = 2πrh
= 2*22/7*15*21
= 1980 sq cm
Answer.
Given : TSA = 3394 2/7 sq cm or 23760/7 cm and Height = 21 cm
Total surface area of the cylinder = 2πr(r + h)
23760/7 = 2*22/7*r(r + 21)
23760 = 44r(r + 21)
23760 = 44r² + 924r
44r² + 924r - 23760 = 0
Dividing it by 44, we get
r² + 21 - 540 = 0
r² + 36r - 15r - 540 = 0
r(r + 36) - 15(r + 36) = 0
(r + 36) (r - 15) = 0
r = 15 or r = - 36
As radius cannot be negative, so radius = 15 cm.
Curved surface area of the cylinder = 2πrh
= 2*22/7*15*21
= 1980 sq cm
Answer.
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