In a class of 25 distinct students, how many different 3-student committees can be formed? (Order of students within the committee does not matter.)
Aptitude
Permutation and Combination
Difficulty: Easy
Choose an option
-
A2200
-
B2300
-
C2400
-
D3200
Answer
Correct Answer: 2300
Explanation
Introduction / Context:Forming committees is choosing subsets, not arranging sequences. The correct tool is combinations C(n, k).
Given Data / Assumptions:
- n = 25 students.
- k = 3 students per committee.
Concept / Approach:Compute C(25, 3) = 25! / (3! * 22!).
Step-by-Step Solution:
C(25, 3) = (252423) / (321) = (60023)/6 = 2300.Verification / Alternative check:Multiplying 2524*23 = 13,800 and dividing by 6 gives 2300 exactly.
Why Other Options Are Wrong:Nearby values (2200, 2400, 3200) reflect arithmetic slips or using permutations.
Common Pitfalls:Confusing ordered selections with unordered committee formation.
Final Answer:2300