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Probability
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Solution —
2019
Question 10
Probability
(a)
(b)
P
(
both red
)
=
10
25
(
9
24
)
=
3
20
∎
(c)
P
(
different colours
)
=
1
−
P
(
same colour
)
=
1
−
(
3
20
+
8
25
(
7
24
)
+
7
25
(
6
24
)
)
=
103
150
∎
(d)
P
(
at least 2 red
)
=
P
(
R
R
R
)
+
P
(
R
R
X
)
+
P
(
R
X
R
)
+
P
(
X
R
R
)
=
10
25
(
9
24
)
(
8
23
)
+
10
25
(
9
24
)
(
15
23
)
+
10
25
(
15
24
)
(
9
23
)
+
15
25
(
10
24
)
(
9
23
)
=
159
460
∎
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