A coin is flipped n times ,where n>/=3
1.Find number of ways to obatin at least 2 heads
一條f5的數學題?5點
2011-05-10 9:06 pm
回答 (1)
2011-05-10 9:11 pm
✔ 最佳答案
1 The no. of ways to obatin at least 2 heads = (total no.) - (no. of getting no head) - (no, of getting one head)
= 2^n - 1 - n
For example, n = 3
HHH, HHT, HTH, THH, no. of ways is 4 as expected
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