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Problems
Contests
National and Regional Contests
Turkey Contests
National Olympiad First Round
2003 National Olympiad First Round
11
11
Part of
2003 National Olympiad First Round
Problems
(1)
P11 [Combinatorics] - Turkish NMO 1st Round - 2003
Source:
5/14/2014
What is the probability of having no
B
B
B
before the first
A
A
A
in a random permutation of the word
ABRAKADABRA
\text{ABRAKADABRA}
ABRAKADABRA
?
<
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(
A
)
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2
3
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(
B
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5
7
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(
C
)
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5
6
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>
(
D
)
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6
7
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(
E
)
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None of the preceding
<span class='latex-bold'>(A)</span>\ \dfrac 23 \qquad<span class='latex-bold'>(B)</span>\ \dfrac 57 \qquad<span class='latex-bold'>(C)</span>\ \dfrac 56 \qquad<span class='latex-bold'>(D)</span>\ \dfrac 67 \qquad<span class='latex-bold'>(E)</span>\ \text{None of the preceding}
<
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(
A
)
<
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>
3
2
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(
B
)
<
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>
7
5
<
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>
(
C
)
<
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>
6
5
<
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a
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x
−
b
o
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d
′
>
(
D
)
<
/
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p
an
>
7
6
<
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x
−
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>
(
E
)
<
/
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>
None of the preceding
probability