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NDA · Maths · Probability
NDA Probability — Formulas 2
Question
1
of 13
1.
An urn has
a
a
a
red and
b
b
b
blue balls;
r
r
r
are drawn at random.
P
(
exactly
k
red
)
P(\text{exactly } k \text{ red})
P
(
exactly
k
red
)
is:
A
(
a
k
)
(
a
+
b
r
)
\dfrac{\dbinom{a}{k}}{\dbinom{a+b}{r}}
(
r
a
+
b
)
(
k
a
)
B
a
k
b
r
−
k
(
a
+
b
)
r
\dfrac{a^{k}\,b^{r-k}}{(a+b)^{r}}
(
a
+
b
)
r
a
k
b
r
−
k
C
(
a
k
)
+
(
b
r
−
k
)
(
a
+
b
r
)
\dfrac{\dbinom{a}{k} + \dbinom{b}{r-k}}{\dbinom{a+b}{r}}
(
r
a
+
b
)
(
k
a
)
+
(
r
−
k
b
)
D
(
a
k
)
(
b
r
−
k
)
(
a
+
b
r
)
\dfrac{\dbinom{a}{k}\dbinom{b}{r-k}}{\dbinom{a+b}{r}}
(
r
a
+
b
)
(
k
a
)
(
r
−
k
b
)
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