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1. A student is to answer 10 out of 13 questions in an examination such that he must choose at least 4 from the first five questions . The number of choices available to him is .
- A. 140
- B. 140
- C. 140
- D. 140
Answer: Option B
Explanation:
If the student answers 4 questions from the first five questions he can choose 6 questions from the remaining 8 questions. Therefore number of combinations will be 5C4 × 8C6 = 140 If the student answers 5 questions from the first five questions he can choose 5 questions from the remaining 8 questions. Which will be 5C5 × 8C5 = 56 Therefore total number of choices = 140 + 56 = 196
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