An open cone with base radius 28cm and perpendicular height 96cm was stretched to form...
MATHEMATICS
WAEC 2013
An open cone with base radius 28cm and perpendicular height 96cm was stretched to form sector of a circle. calculate the arc of the sector (Take \(\pi = \frac{22}{7}\))
- A. 8800cm2
- B. 8448cm2
- C. 4400cm2
- D. 4224cm2
Correct Answer: A. 8800cm2
Explanation
L2 = 962 + 282
= 9216 + 784
= 10000
L = \(\sqrt{10000}\)
= 100cm
curved surface area = \(\pi r l\)
= \(\frac{22}{7} \times 28 \times 100\)
= 8800cm2
area of cone = area of sector
area of sector = 8800cm2
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