This is a classic combinations problem that trips up many students. Let me walk you through the key insight that makes this question much clearer.
The Critical Insight:The moment you choose 3 people for the lead team, the remaining 3 people automatically become the backup team. You're not making two separate choices - you're really just asking "In how many ways can I select 3 people from 6 for the lead team?"
Let's think about this step by step:Step 1: Understand what we're really selectingWhen the problem says "divide 6 employees into teams of 3 each," it sounds complicated. But notice that once you pick Alice, Bob, and Charlie for the lead team, Diana, Eve, and Frank must be the backup team. There's no separate choice to make.
Step 2: Recognize this as a combination problemSince we're selecting 3 people from 6, and the order within the team doesn't matter (Alice-Bob-Charlie is the same lead team as Bob-Alice-Charlie), this is a combinations problem, not permutations.
Step 3: Apply the combination formulaWe need \(C(6,3) = \frac{6!}{3! \times 3!}\)
Let's calculate: \(C(6,3) = \frac{6 \times 5 \times 4}{3 \times 2 \times 1} = \frac{120}{6} = 20\)
Step 4: Verify our logicEach selection of 3 people creates exactly one unique lead team and one unique backup team. Since we're only counting lead teams (not backup teams), our answer is 20.
Answer: (D) 20The key breakthrough here is recognizing that you're not dividing into two separate groups - you're selecting one group, and the other is automatically determined. This insight applies to many similar "division" problems on the GMAT.
You can check out the
comprehensive solution on Neuron by e-GMAT to master the systematic framework for all team selection problems and learn about the common trap answers that students fall into. You can also explore detailed solutions for
similar official questions to build consistent accuracy across all combination problems.