Find the length of the slant height of a cone with a radius of 15 cm and a surface area of 1884 square cm.
surface area of cone= pi *r *l \[\pi \times 15 \times l=1884,l=\frac{ 1884 }{ 15 \pi }=\frac{ 1884 }{ 15 \times 3.14 }=\frac{ 1884\times 100 }{ 15 \times 314 } =40\] |dw:1462912341222:dw|
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\(\large A_{cone} = \pi r^2 + \pi r l\) Let's start with the surface of the base. \(\large A_{base} = \pi r^2 = \pi \times (15~cm)^2 = 707~ cm^2\) Subtract 707 cm^2 from the surface area, and you have the lateral surface area. Lateral surface area = 1884 cm^2 - 707 cm^2 = 1177 cm^2 The lateral surface area = \(\pi r l\), and r = 15 cm. \(\pi r l = 1177~cm^2\) \(3.14159 \times 15~cm \times l = 1177~cm^2\) Solve for \(l\)
l=25
Correct.
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