The formula for the volume of a frustum of a cone is
V = (1/3)π·(R² + r² +r·R)·h
where R and r are the radii of the circular faces.
For your figure, R = 4.2, r = 2.5, h = 14. Filling in the given numbers, you have
V = (π/3)(4.2² +2.5² +4.2·2.5)·14 ≈ 504.18
It looks like the appropriate choice is probably
B. 503.77
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Sometimes the answers to these problems are figured using incorrect rounding and inappropriate values of π. It looks like this answer key was simply miscalculated.
