Correct Answer - B
Let
A
i
A
denote the event of getting 1, first time, in
i
t
h
i
throw.
Clearly,
p=Probability of getting 1 in a throw
=
1
6
=
q=Probability of not getting 1 in a throw
=
5
6
=
Required probability
=
P
(
A
2
∪
A
4
∪
A
6
∪
.
.
)
=
=
P
(
A
2
)
+
P
(
A
4
)
+
P
(
A
6
)
+
P
(
A
8
)
+
.
.
=
=
q
p
+
q
3
p
+
q
5
p
+
q
7
p
+
.
.
=
q
p
1
−
q
2
=
5
/
36
1
−
25
36
=
5
11
q
