Question

the total surface area of a right circular cone of slant height 13 cm is 90πcm² find its radius
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Answer 1

Step-by-step explanation:

total surface area=

$\pi$

r(l+r)

90

$\pi$

=

$\pi$

r(l+r)

90=r(13+r)

90=13r +r square

${r}^{2}$

+13r-90=0

${r}^{2}$

+18r-5r-90

r(r+18)-5(r+18)

r=5