Question on: WAEC Mathematics - 2014
The area of a sector a circle with diameter 12cm is 66cm2. If the sector is folded to form a cone, calculate the radius of the base of the cone [Take \(\pi = \frac{22}{7}\)]
A
3.0cm
B
3.5cm
C
7.0cm
D
7.5cm
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Correct Option: B
diameter = 12cm
radius = \(\frac{12}{2}\)cm = 6cm
area of sector = 66cm2
area of sector = area of cone
66 = \(\pi rl\)
66 = \(\frac{22}{7} \times r \times 6\)
divide both sides by 6
11 = \(\frac{22}{7}r\)
22r = 11 x 7
r = \(\frac{77}{22}\)
= 3.5cm
radius = \(\frac{12}{2}\)cm = 6cm
area of sector = 66cm2
area of sector = area of cone
66 = \(\pi rl\)
66 = \(\frac{22}{7} \times r \times 6\)
divide both sides by 6
11 = \(\frac{22}{7}r\)
22r = 11 x 7
r = \(\frac{77}{22}\)
= 3.5cm
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