b***k
发帖数: 2673 | 1 ☆─────────────────────────────────────☆
yuyy (yyy) 于 (Fri May 8 17:38:00 2009) 提到:
1. escalator problem
two persons are running on escalator the same time. each time A go 2 stairs,
B go 3 stairs, finally A reached the top with 25 steps, and B got it with 20
steps.ask how many stairs the escalator has to be visible?
(not sure if I caught the condtions right, but the answer is 50.)
2. One stock, currently price is 10, one year later, it either be 12
with 0.6 probability or 8 with 0.4 probabi |
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