Permutations & Combinations
Counting Geometric Configurations
Grade 11
Question:
<p>The number of ways of selecting two coplanar and perpendicular lines from the edges and face diagonals of a cube is equal to</p>
Step-by-Step Solution
Key Concept: Identify coplanar perpendicular pairs among edges and face diagonals
<p>Lines are coplanar if they lie in the same plane. Among edges and face diagonals of a cube, we need pairs that are both coplanar and perpendicular. The number of such pairs is 54.</p>
Correct Answer: S