12 multiple-choice questions, progressively harder.
Similar solids have volumes 192 and 648 cubic cm, in original:image order. An original edge is 10 cm long. How long is its image?
Solution
Correct answer: C
Recover the length factor with a positive cube root.
Similar solids have total surface areas 500 and 980 square cm, in original:image order. The original volume is 500 cubic cm. What is the image volume?
Correct answer: A
Surface areas give the square of the length factor, not the volume factor.
A similar image has 27/6427/6427/64 of the original volume. Its total surface area is 162 square cm. What is the original total surface area?
Correct answer: D
The image-to-original length factor is 3/4, so the surface factor is 9/16. Reverse that factor to recover the original.
Every length of a solid increases by 20%20\%20%. What is the percentage increase in its volume?
Correct answer: B
A 20 percent length increase gives multiplying factor 1.2. Cube it, then subtract the original one whole.
A similar image has 12.5%12.5\%12.5% of the original volume. What fraction of the original surface area does it have?
The volume factor is 1/8. Its positive cube root is 1/2; square that for surface area.
A closed cube has edge 8 cm. What is its surface-area-to-volume ratio?
Divide the six face areas by the cube volume.
Solid A and solid B are similar. B has length factor 5/25/25/2 from A. A has surface-area-to-volume ratio 1.5 cm−11.5\text{ cm}^{-1}1.5 cm−1. What is B's ratio?
The ratio changes by the reciprocal of the length factor.
The unit is per centimeter.
A closed rectangular box is 2 by 3 by 4 cm. Only the 4 cm height changes to 12 cm. What is the new total surface area?
The bases keep their areas while the four side faces become taller. Use the actual dimensions.
A right cylinder initially has radius 3 cm and height 5 cm. Its radius doubles while height stays fixed. What are the image-to-original volume and total surface-area factors, in that order?
This is not a similar resize. The original volume is 45 pi and new volume 180 pi cubic cm, so volume has factor 4.
The surface-area factor is 132/48=11/4132/48=11/4132/48=11/4.
A rectangular prism has dimensions 4 by 7 by 9 cm. A second has dimensions 10 by 17.5 by 22.5 cm, with corresponding dimensions in order. What is the second-to-first volume factor?
Each corresponding dimension has factor 5/2, so these prisms are similar.
Two similar solids have corresponding lengths 20 mm and 3 cm, in original:image order. What is the image-to-original surface-area factor?
Convert 3 cm to 30 mm before forming the length ratio.
Similar solids have total surface areas 72 and 200 square cm, in original:image order. What is the image-to-original volume factor?
The surface-area ratio is 25/9. Its positive square root gives the length factor.
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