a)all are heads
b)at least one is head
c)exactly one is tail
更新1:
Any explaination?
easy maths
2008-08-14 7:09 pm
1)A coin is thrown twice.Find the probability that
a)all are heads
b)at least one is head
c)exactly one is tail
a)all are heads
b)at least one is head
c)exactly one is tail
回答 (2)
2008-08-24 1:05 am
✔ 最佳答案
(a)1st way of thinking:
possible cases: HT, HH, TH, TT
Pr[all heads] = correct case / possible case = 1/4
2nd way of thinking (assume the two outcomes are independent):
Pr[head]=1/2
Pr[both head] = Pr[1st head] x Pr[2nd head] = (1/2)^2 = 1/4
(b)
Pr[at least one head]
= 1-Pr[no head]
= 1-Pr[all tails]
= 1-1/4 = 3/4
(c)
Possible cases: HH, [HT], [TH], TT
Pr[exactly one tail]
=2/4 =1/2
參考: myself
2008-08-14 7:20 pm
a) 1/2 + 1/2 = 1/4
b) 1/2 x 1/2 = 1/4
c) 1/2
b) 1/2 x 1/2 = 1/4
c) 1/2
收錄日期: 2021-05-03 11:38:54
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