Volume of a sphere is four-thirds pi r cubed. Diameter 6 means r = 3, so volume is (4/3)π(27) = 36π. Volume as a set is in area and volume.
Radius, not diameter
Halve the diameter first. Surface area of a sphere is 4πr², a different formula, in surface area. A cone uses a different shape, in volume of a cone.
The short list is in ACT Math formulas.
The bottom line
(4/3)πr³. Cube the radius, not the diameter.
Start practicing
Start with a free diagnostic, then drill your weak spots with 15-question quizzes and track how you're doing across Reading, English, and Math. Compare plans whenever you're ready to go further.
This article offers general ACT prep guidance. The ACT can change from year to year, including its format, scoring, policies, test dates, and fees, so always confirm the latest details on the official ACT website at act.org before you make decisions. ACT® is a registered trademark of ACT, Inc. thirty-six is not affiliated with, endorsed by, or sponsored by ACT.