概率一問probability

Actually you need not think too difficultly...

^_^

For 3 letters to be put in the same box...
(A) Letter 1 can be put in any box
(B) Letter 2 MUST be put in the box that contain letter 1
(C) Letter 3 MUST be put in the box that contain letter 1

P(all 3 letters to be put in the same box)
=P(A, B, C happens together)
=P(Letter 1 put in any box) x P(Letter 2 put in the box that contain letter 1) x P(Letter 3 put in the box contain letter 1)
= 1 x 1/4 x 1/4
= 1/16

(1/4)^3
=1/64

2007-10-21 10:16:01 補充：
sorry..計錯了..太大意P=probability有abcd四個box當你放係a box到先啦每封letter放係a box ge P係1/4第一封:1/4如果第二封都要放係a box到ge P:1/4 x 1/4 = 1/16如果第三封都要放係a box到ge P:1/4 x 1/4x 1/4 = 1/64即係話all the letters are put in the a box:1/64but依家有abcd 四個box 每個ge P:1/64the answer is 1/64 x 4 = 1/16

probability that all 3 letters are put in the same box
= (1/4)^3
= 1/64

2007-10-19 17:56:02 補充：
1/4 means 1 box out of the 4 boxes,^3 means to the power 3, because the same box is chosen 3 times.