Compute volume and surface area of solids (prisms, cylinders, pyramids, cones, spheres).
Choose the solid and the measure first: inside space for volume, outer covering for surface area.
核心知识
Volume measures space inside a solid; surface area measures the exposed outside. Choose the right formula first, then substitute carefully with the correct radius, height, or slant height.
深入理解
Rule: Start by classifying the solid and deciding whether the question asks for inside space or outside covering. Prisms and cylinders use base area times height. Pyramids and cones use one-third of the matching prism or cylinder volume. Surface area adds the areas of the exposed faces, so you have to know which dimensions control each face.
On ACT, once the formula choice is right, the arithmetic is usually straightforward. The bigger trap is using diameter instead of radius or confusing height with slant height.
示例解析
A right circular cylinder has radius
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