為什麼乘兩路公共汽車的次數會相差得很遠？

because 105 always arrive first !!
---------------------------------------------------------------------------------------------------------------------
e.g. 小明 wait the bus at 12:55pm ,105 arrive at 1:00pm, and 101 arrive at 1:02pm,so
小明 take 105.
e.g. 小明 wait the bus at 1:10pm, 105 arrive at 1:15pm, and 101 arive at1:17pm
小明 take 105 again.
the same situation in most of the time, 小明always take 105 because it always come first!!

小明 take 101 when the 105 has just gone away only, it has much lower probability, e.g. only at 1:01pm or 1:16pm !!

so, although the frequency of both bus are 15mins, 小明 much more often to take 105.

2007-01-02 17:46:00 補充：
if the difference of the arrival time of those buses is 7.5 mins or 0 mins, the rate would be 50% 50%.

but it does not mention that in the long run, the probability of taking either 101 or 105 is equal since all situations are in random.