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JEE Main Math Class 12 Statistics Part 2 Questions
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© examsnet.com
Question : 25
Total: 28
Let the positive numbers
a
1
,
a
2
,
a
3
,
a
4
and
a
5
be
in a G.P. Let their mean and variance be
31
10
and
m
n
respectively, where
m
and
n
are co-prime. If the mean of their reciprocal is
31
40
and
a
3
+
a
4
+
a
5
=
14
, then
m
+
n
is equal to ______.
[12-Apr-2023 shift 1]
Your Answer:
Validate
Solution:
Let
a
r
2
,
a
r
,
a
,
ar
,
ar
2
Given
a
r
2
+
a
r
+
a
+
ar
+
ar
2
=
5
×
31
10
.
.
.
(
1
)
And
r
2
a
+
r
a
+
1
a
+
1
ar
+
1
ar
2
=
5
×
31
40
.
.
.
(
2
)
(
1
)
÷
(
2
)
a
2
=
4
⇒
a
=
2
∴
r
+
1
r
=
5
∕
2
(
a
≠
−
2
)
⇒
r
=
2
∴
Now
1
2
,
1
,
2.4
,
8
∴
Now
1
2
,
1
,
2.4
,
8
∴
σ
2
=
Σ
x
2
N
−
(
Σ
x
N
)
2
=
186
25
=
M
N
⇒
211
=
m
+
n
© examsnet.com
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