A sector is cut off from a circle radius 8.2cm to form a cone, if the radius of the resulting cone is 3.5cm, calculate the curved surface area of the cone. [take π = 22/7]

  • A 11.25cm2
  • B 12.83cm2
  • C 22.0cm2
  • D 67.2cm2
  • E 90.2cm2
waec 1989mathematics

The correct answer is E. 90.2cm2

r = 3.5 cm; l = 8.2 cm.

Curved surface area = \(\pi rl\)

= \(\frac{22}{7} \times \frac{7}{2} \times \frac{41}{5}\)

= 90.2 cm\(^2\)

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