pls help ! maths probability
2008-12-24 2:20 am
A fair $5 coin is tossed three times. Find the probability of getting exactly 2 Heads
回答 (3)
2008-12-25 10:26 am
✔ 最佳答案
P(Get 2 heads out of 3 times)= P(HHT) + P(HTH) + P(THH)
= (1/2 x 1/2 x 1/2) + (1/2 x 1/2 x 1/2) + (1/2 x 1/2 x 1/2)
= 3(1/2 x 1/2 x 1/2)
= 3/8 (or 37.5%)
The probaaility of getting exactly 2 Heads is 3/8.
參考: Myself
2008-12-24 3:09 am
你可畫 tree diagram 黎塭
／H (H, H, H)
／H
＼T (H, H, T)
H
＼ ／H (H, T, H)
T
＼T (H, T, T)
／H (T, H, H)
／H
＼T (T, H, T)
T
＼ ／H (T, T, H)
T
＼T (T, T, T)
∴ The probability of getting exactly 2 heads is 3/8.
／H (H, H, H)
／H
＼T (H, H, T)
H
＼ ／H (H, T, H)
T
＼T (H, T, T)
／H (T, H, H)
／H
＼T (T, H, T)
T
＼ ／H (T, T, H)
T
＼T (T, T, T)
∴ The probability of getting exactly 2 heads is 3/8.
參考: 自己計
2008-12-24 3:03 am
You can list all cases
Let H : Head ; T : Tail
Possible Combinations
HHH HHT HTH HTT TTT TTH THT THH
So the probability of getting exactly 2 Heads
=3/8
2008-12-23 19:45:26 補充：
http://img103.imageshack.us/img103/4804/ykprobabilityld7.png
Tree diagram
Let H : Head ; T : Tail
Possible Combinations
HHH HHT HTH HTT TTT TTH THT THH
So the probability of getting exactly 2 Heads
=3/8
2008-12-23 19:45:26 補充：
http://img103.imageshack.us/img103/4804/ykprobabilityld7.png
Tree diagram
收錄日期: 2021-04-25 16:58:52
原文連結 [永久失效]:
https://hk.answers.yahoo.com/question/index?qid=20081223000051KK01423