Cone cut to parallel to base and ratio of volume is 1/27
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When a cone is cut with a plane parallel to its base, it gives us two pieces.
I assume the ratio of the two pieces is 1 : 27.
One is a smaller cone on top of the previous cone. The other part is called a frustum.
Let the height of the top part (smaller cone) = h
its radius (base) = r.
its volume = π/3 r² h
Height of frustum = H - h.
Height of the original big cone = H
its base radius (bigger base of frustum) = R.
its volume = π/3 R² H - π/3 r² h
We know that (by similar triangles principles)
r : R = h : H
h = H r / R
Ratio of volumes
1 : 27 = r² h : (R² H - r² h)
1/27 = r² H r / R : (R² H - r² H r / R)
1/27 = r³ : (R³ - r³)
So 27 r³ = (R³ - r³)
28 r³ = R³
r/R = ∛28.
Same way h/H = ∛28
I assume the ratio of the two pieces is 1 : 27.
One is a smaller cone on top of the previous cone. The other part is called a frustum.
Let the height of the top part (smaller cone) = h
its radius (base) = r.
its volume = π/3 r² h
Height of frustum = H - h.
Height of the original big cone = H
its base radius (bigger base of frustum) = R.
its volume = π/3 R² H - π/3 r² h
We know that (by similar triangles principles)
r : R = h : H
h = H r / R
Ratio of volumes
1 : 27 = r² h : (R² H - r² h)
1/27 = r² H r / R : (R² H - r² H r / R)
1/27 = r³ : (R³ - r³)
So 27 r³ = (R³ - r³)
28 r³ = R³
r/R = ∛28.
Same way h/H = ∛28
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