Evaluating a permutation — Aptitude Question
Evaluating a permutation: What is the value of P(6, 3)? Answer and worked solution on CodeKairo.
- Topic: Permutations & Combinations
- Section: Quantitative Aptitude
- Difficulty: Easy
- Time target: 45 seconds
Question
What is the value of P(6, 3)?
Options
- 18
- 20
- 120
- 216
Show the answer and the worked solution
Correct answer: C. 120
Worked solution
- P(6,3) = 6 × 5 × 4 = 120.
Answer: 120.
The idea
Permutations count ordered selections, so no division by r!. C(6,3) would be 20, which is offered.
Shortcut. Take 6! = 720 and divide by 3! = 6 for the three unused places: 720 ÷ 6 = 120.
Common trap. "216" — using 6³, which lets the same item be used again; a permutation takes each item at most once, so 6 × 5 × 4.
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