Two triangular pyramids are similar. The volume of the larger pyramid is 729 cm3 , and the volume of the smaller pyramid is 64 cm3. If the perimeter of the base of the smaller pyramid is 8 cm, what is the perimeter of the base of the larger pyramid?

For similar pyramids, the ratio of their volumes is the cube of the ratio of corresponding lengths. The volume ratio is 729:64, so the length ratio is 9:4 because 9³ = 729 and 4³ = 64. The larger base perimeter is 8 × 9/4 = 18 cm, so the correct choice is 18 cm.

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