Mathematics
NULL
Medium
Question
A group of 10 is chosen from 12 seniors and 10 juniors and must include at least one senior. How many ways are there?
A
22C10
B
22C10 + 1
C
22C9 + 10C1
D
22C10 - 1
✓ Official correct answer
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A
22C10
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B
22C10 + 1
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C
22C9 + 10C1
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D
22C10 - 1
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Explanation
Total ways from 22 people: ²²C₁₀; exclude all juniors (1 way) ⇒ ²²C₁₀ − 1.