MultiplicationPrinciple AMC8 Basic
2015


Problem - 2569
How many pairs of parallel edges, such as $\overline{AB}$ and $\overline{GH}$ or $\overline{EH}$ and $\overline{FG}$, does a cube have?

There are three groups of parallel edges each of which contains $4$ edges. Therefore, the answer is $$3\times C_4^2 = \boxed{18}$$

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