A cone is made from a sector of circle of radius 14cm and angle of 90o. What is the area of the curved surface of the cone? (Take x = 22/7)

  • A 22cm2
  • B 38.5cm2
  • C 77cm2
  • D 154cm2
  • E 308cm2
waec 1988mathematics

The correct answer is D. 154cm2

Length of arc = θ/360 * 2πr

=> r = 90/360 * 14/4 = 3.5

slant height t = 14cm

curved surface area of cone = πrl

=> 3.142 x 3.5 x 14 = 153.95

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