12 multiple-choice questions, progressively harder.
Two solids are known to be similar. The original total surface area is 150 square cm and volume is 125 cubic cm. The image volume is 1000 cubic cm. What is the image surface-area-to-volume ratio?
Solution
Correct answer: D
The volume factor 8 gives length factor 2. Surface area has factor 4.
A similar image has surface-area-to-volume ratio 4/54/54/5 of the original ratio, with both expressed in the same unit. What is its image-to-original volume factor?
Correct answer: B
The ratio factor is the reciprocal of the length factor, so the length factor is 5/4.
A similar image has 69%69\%69% more total surface area than its original. What percentage of the original volume is the image volume?
Correct answer: C
The surface factor is 1.69. Take its positive square root, then cube.
This is 219.7 percent of the original volume, a 119.7 percent increase.
A cube has edge 4 cm. Candidate A is a cube of edge 12 cm. Candidate B is a rectangular box 4 by 4 by 108 cm. Both candidates have the same volume. Which statement is correct?
Correct answer: A
Candidate A uses length factor 3 in every direction. B keeps two dimensions fixed and changes the third by factor 27.
Equal volumes do not supply a common length factor.
A closed right cylinder has radius 2 cm and height 8 cm. Its volume must become 4 times as large. Plan A resizes the entire cylinder uniformly. Plan B keeps the radius fixed and changes only height. Which pair gives the two new heights, in Plan A then Plan B order?
Plan A has a cubic volume factor, so its length factor is the positive cube root of 4. Plan B keeps the base area fixed, so height must have factor 4.
Solids A and B are similar. Their surface-area ratio A:B is 4:94:94:9. Their combined volume is 665 cubic cm. What is B's volume?
The length ratio is 2:3, so the volume ratio is 8:27. There are 35 volume-ratio parts altogether.
A similarity takes an original solid to an image with 125/216125/216125/216 of its volume. The image surface area is 250 square cm. What is the original surface area?
The length factor is 5/6, so the surface-area factor is 25/36. Divide the known image surface area by that factor.
An original closed right cylinder and its image have corresponding radii 5 and 10 cm and heights 6 and 12 cm, respectively, in original:image order. Their total surface-area ratio is 1:4. Which image-to-original volume factor is consistent with all these measurements?
Both radius and height use factor 2, establishing similarity for these right cylinders. The squared surface factor agrees.
A closed rectangular box is 3 by 5 by 6 cm. Its height alone is multiplied by a positive factor ttt, with the 3 by 5 cm base fixed. Which expression gives its new total surface area in square cm?
The pair of base faces keeps area 30 square cm. The four side faces have their original combined area 96 square cm multiplied by t.
Simplifying gives 30+96t30+96t30+96t.
A positive uniform resize doubles a solid's surface-area-to-volume ratio. What happens to its total surface area?
Doubling this ratio requires length factor 1/2, because the ratio uses the reciprocal length factor.
A solid is claimed to be a similar image of another with length factor 3/23/23/2. Its measured total surface area has factor 9/49/49/4, but its measured volume has factor 333. What can be concluded if all measurements are exact and corresponding boundaries match?
The length factor requires volume factor 27/8, which is not 3. The surface factor alone cannot repair that inconsistency.
A solid has surface area 0.54 square m and volume 0.027 cubic m. What is its surface-area-to-volume ratio expressed per centimeter?
First form the ratio in the given units.
This is 20 per meter. Since one meter is 100 cm, 20/(100 cm)20/(100\text{ cm})20/(100 cm) is 0.2 cm−10.2\text{ cm}^{-1}0.2 cm−1.
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