There are 10 distinct oranges in a basket. In how many ways can 3 oranges be chosen? (Treat oranges as distinct items; order of selection does not matter.)
Aptitude
Permutation and Combination
Difficulty: Easy
Choose an option
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A125
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B140
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C110
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D120
Answer
Correct Answer: 120
Explanation
Introduction / Context:This is an elementary combinations problem: selecting k items from n distinct items without regard to order is counted by C(n, k).
Given Data / Assumptions:
- n = 10 distinct oranges.
- k = 3 oranges chosen.
- Order is irrelevant.
Concept / Approach:Use C(10, 3) = 10! / (3! * 7!).
Step-by-Step Solution:
C(10, 3) = (1098) / (321) = 120.Verification / Alternative check:Check with symmetry: C(10, 3) = C(10, 7) also equals 120.
Why Other Options Are Wrong:125, 140, and 110 are common miscomputations; 120 is the unique correct combination count.
Common Pitfalls:Using permutations (10P3) instead of combinations, thereby overcounting by 3!.
Final Answer:120