Signals from flags — Aptitude Question
Signals from flags: How many different signals can be made using 3 flags out of 5 different flags, where order… Answer and worked solution on CodeKairo.
- Topic: Permutations & Combinations
- Section: Quantitative Aptitude
- Difficulty: Medium
- Time target: 60 seconds
Question
How many different signals can be made using 3 flags out of 5 different flags, where order matters?
Options
- 10
- 20
- 60
- 125
Show the answer and the worked solution
Correct answer: C. 60
Worked solution
- P(5,3) = 5 × 4 × 3 = 60.
Answer: 60.
The idea
Signals depend on the order of the flags, so this is a permutation. C(5,3) = 10 would be the answer if order were irrelevant.
Shortcut. Fill the three positions in order: 5 choices, then 4, then 3 — 60.
Common trap. "125" — allowing a flag to be used more than once (5 × 5 × 5); there are only 5 different flags, each used once.
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