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Byju's Answer
Standard VIII
Mathematics
Introduction to Statistics
if the mean o...
Question
if the mean of five observations x,x+2,x+4,x+6,x+8 is 11,find the mean of first three observations. answer =9.
but how?
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Solution
We
know
that
:
Mean
of
observations
=
sum
of
observations
number
of
observations
The
given
5
observations
are
:
x
,
x
+
2
,
x
+
4
,
x
+
6
and
x
+
8
Mean
of
5
observations
=
x
+
x
+
2
+
x
+
4
+
x
+
6
+
x
+
8
5
⇒
11
=
5
x
+
20
5
⇒
5
x
+
20
=
55
⇒
5
x
=
55
-
20
⇒
5
x
=
35
⇒
x
=
35
5
=
7
Now
the
first
3
observations
are
:
7
,
7
+
2
and
7
+
4
i
.
e
.
7
,
9
,
11
.
Mean
of
first
3
observations
=
7
+
9
+
11
3
=
27
3
=
9
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Q.
If the mean of five observations x, x + 2, x + 4, x + 6, x + 8 is 11. Find the mean of first three observations
Q.
If the mean of five observations
x
,
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+
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,
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,
x
+
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,
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is
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Q.
If the mean of five observations x, x+2, x+4, x+6, x+8, is 11, then the mean of first three observations is
(a) 9
(b) 11
(c) 13
(d) none of these