Probability

P(5 heads and 5 tails)

= (10C5)(1/2)^10

= 252 / 1024

= 63/256

Example :

HHHHHTTTTT
HHHHTHTTTT
HHHTTHTTTH

10 positions to put 5H or 5T,hence 10C5 ways



2009-11-26 22:04:38 補充：
10C5即係10個拿5個出來(不重複)的方法數,

10C5 = 10*9*8*7*6 / (5*4*3*2*1)

P(HHHHHTTTTT) = (1/2)^10

P(HTHTHTTHHT) = (1/2)^10

.......................

共 10C5 個所以 P(E) = 10C5 * (0.5)^10