How many different 3-letter codes can be formed from 7 distinct letters if no letter is repeated and order matters?
Answer and explanation
Correct answer: A. 210
- Step 1: Order matters, so use permutations: nPr = n!/(n - r)!. Step 2. 7P3 = 210. Answer: 210. Why not the others: 35: That ignores the order. 343: That allows repeats. 21: That multiplies n by r.
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