How many three-digit numbers can be formed from the digits 2, 3, 4, 5, 6, 7, and 8 if repetition is not allowed?
- 420
-
210
- 120
- 35
The correct answer is: B
Explanation
Since repetition is not allowed, we can use permutation for this question.
\(^7_3 P\) = \(\frac{7!}{(7 - 4)!}\) = 210
OR
Choose the First Digit: 7 options (2-8).
Choose the Second Digit: 6 options remaining.
Choose the Third Digit: 5 options remaining
Total Combinations:
Total = 7 × 6 × 5 = 210.