There will be 5 cases and each case will be equally probable so lets find out the probability of getting 1 red ball in each case.
Case 1= 5 Red balls and 0 green ball.
P
(
r
e
d
b
a
l
l
)
=
1
.
P
Case 2 = 4 Red balls and 1 green ball.
P
(
r
e
d
b
a
l
l
)
=
4
5
P
Case 3= 3 Red balls and 2 green ball.
P
(
r
e
d
b
a
l
l
)
=
3
5
P
Case 4= 2 Red balls and 3 green balls.
P
(
r
e
d
b
a
l
l
)
=
2
5
P
Case 5= 1 Red ball and 4 green balls.
P
(
r
e
d
b
a
l
l
)
=
1
5
P
now since each case is equally probable , probability of each case=
1
5
1
We have to find the probability of Case 1 =
(
1
5
)
×
1
1
5
×
(
1
+
4
5
+
3
5
+
2
5
+
1
5
)
=
1
3
(
.
