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[求助]OG-PS 316,421

OG –S
316. Pat will walk from intersection X  to intersection Y along a route that is confined to the square grid of 4 streets and 3 avenues, how many routes from X to Y the minimum possible length.  
a) 6
b) 8
c) 10
d) 14
e) 16
question: Do any body have easier way to solve this kind of problem?

421. If a number between 0 and ½ is selected at random, which of the following will the number most likely be between?
a) 0 and 3/20
b) 3/20 and 1/5
c) 1/5 and ¼
d) ¼ and 3/10
e) 3/10 and ½

question: I can not understand the explaination in OG. Who can do me a favor to give me some more details?

Thanks in advance.
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I guess the first one has  a easier way,

how about this:

P(5,5)/{P(3,3)*P(2,2)}=10.

TOP

To Lisa, your explaination is understandable. Thanks!

Happy New Year!

TOP

hey Jean
for your first Qu I am afraid I have no better method
but for your second Qu , try to think of it this way
since 'a number between 0 and ½ is selected at random'
every number has the same possibility to be chosen
so the larger the range is , the more likely a number between the it will be chosen
you get what I mean ?

^^
haPPy nEw YeAR
Concentrated and Diligent

TOP

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