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# Gcse question help please Watch

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1. The question is that:

TOTAL surface area of cone is equal to the surface area of the sphere workout the length of the slanted height.

The book answer is 12, but i get 12 and 9

my answer for 12 is (but this does not include the radius)

pi*r*l=4*pi*r^2
3*pi*l=36*pi
l=12

for 9 i use the total surface are of the cone meaning that i also incluse the circle at the bottom as it say total s.a.

But when i use the total i get 9 when i use the curved suface i get 12 is this an error in the book or am i just missin something.

Thanks.........
2. Did they say anywhere that it was an open cone? If it was a closed cone you would include the circle at the base

Updated: February 29, 2012
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