The total surface area of a cone is 616 cm² and its base radius is 7 cm. Find the slant height.
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Correct answer: B
Explanation
Total surface area = 616 cm²
radius r = 7 cm
According to the formula:
Total surface area = πr(l + r)
616 = 22/7 × 7 × (l + 7)
616 = 22(l + 7)
l + 7 = 616 / 22
l + 7 = 28
l = 21 cm