SOLUTION: slant height of frustum of cone is 5cm .if difference between radius of its two circular ends is 4cm .write the height of frustum.

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Question 694290: slant height of frustum of cone is 5cm .if difference between radius of its two circular ends is 4cm .write the height of frustum.
Answer by MathLover1(20849) About Me  (Show Source):
You can put this solution on YOUR website!


make a sketch of its cross section and draw in the height
I see a right -angled triangle with height h, so that
l%5E2=h%5E2%2B%28R-r%29%5E2...where R and r are radii of the base, h is height, and l is slant_height

given:
l=5cm
the difference between radius of its two circular ends is %28R-r%29=+4cm
l%5E2=h%5E2%2B%28R-r%29%5E2....plug in given values
5%5E2=h%5E2%2B4%5E2
25+=h%5E2+%2B+16
h%5E2+=+25-16
h%5E2+=+9
highlight%28h+=+3cm%29
as you can see, the infamous 3-4-5 right-angled triangle