Surface area measures the outside of a solid in square units, while volume measures the space inside in cubic units, and Solid geometry (surface area, volume) checks both.
For a rectangular box, surface area adds the areas of three pairs of matching faces. Formulas for spheres, cones and cylinders are usually given in the question, so the work is substituting and solving, often backward from a known volume or area to find a radius.
A frequent slip is forgetting to take a square root after solving for r squared. Answer choices also tempt with the result of counting only three faces of a box instead of all six.
Sample questions
Pick an answer to see whether it is right — nothing is saved, and nothing needs an account.
Question 1Easier
A closed rectangular box measures 6 cm by 5 cm by 4 cm. What is the total surface area, in square centimeters, of the box?
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Answer: C — 148
Surface area is 2(6⋅5+6⋅4+5⋅4)=2(30+24+20)=148. Omitting the factor of 2 or computing volume 6⋅5⋅4=120 yields common distractors.
Question 2Mid
A spherical ornament has surface area 100π square centimeters. What is the radius, in centimeters, of the ornament? (Use SA=4πr2.)
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Answer: B — 5
4πr2=100π ⇒ r2=25 ⇒ r=5.
Question 3Mid
An ice-cream cone has volume 48π cubic centimeters and height 9 centimeters. What is the radius of its circular base?
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