# Anyone here is good at Probability? I can't get the answer for this question...

• September 14th 2009, 11:52 AM
daominhhai129
Anyone here is good at Probability? I can't get the answer for this question...
• September 14th 2009, 12:06 PM
Plato
Quote:

Originally Posted by daominhhai129

Let R be a right move: $P(R)=\frac{2}{6}$.
Let L be a left move: $P(L)=\frac{4}{6}$.
To end at B in three moves, we need RRL, RLR, or LRR.
Each of those has the same probability and $P(RRL)=\frac{2}{6}\cdot \frac{2}{6}\cdot\frac{4}{6}$
• September 14th 2009, 12:12 PM
daominhhai129
thank you very much..but my answer sheets say it's 2/9....i don't know whether my answer sheet is wrong or i do wrongly...
• September 14th 2009, 12:20 PM
Plato
Quote:

Originally Posted by daominhhai129
my answer sheets say it's 2/9..

No the answer sheet is correct.
$3P(RRL)=3\left(\frac{2}{6}\cdot \frac{2}{6}\cdot\frac{4}{6}\right)=\frac{2}{9}$
• September 14th 2009, 12:22 PM
daominhhai129
oh haha..thank you thank you..i'm so stupid..ya..now i can understand..thanks