Committee from officers and jawans (at least one officer): From 4 officers and 8 jawans, how many 6-person committees include at least one officer?
Aptitude
Permutation and Combination
Difficulty: Easy
Choose an option
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A896
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B986
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C886
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D996
Answer
Correct Answer: 896
Explanation
Introduction / Context:We must count 6-person committees that include at least one officer. The complement (no officer) is easier to compute and subtract from the total committees possible.
Given Data / Assumptions:Total people = 12 (4 officers + 8 jawans); committee size = 6.
Concept / Approach:Total − (no officer). No-officer committees must be formed entirely from jawans.
Step-by-Step Solution:
Total committees = C(12, 6) = 924No-officer committees = C(8, 6) = 28Required = 924 − 28 = 896Verification / Alternative check:Summing by officer count (1 to 4) reproduces 896.
Why Other Options Are Wrong:986, 886, 996 are off by ignoring the complement or miscomputing combinations.
Common Pitfalls:Accidentally allowing 0 officers; arithmetic slips on C(12,6) or C(8,6).
Final Answer:896