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UPSC CDS Math Statistics Questions
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© examsnet.com
Question : 19
Total: 63
The arithmetic mean of 11 observations is 11. The arithmetic mean of the first 6 observations is 10.5 and the arithmetic mean of the last 6 observations is 11.5. What is the sixth observation ?
[2018 CDS-I]
10.0
10.5
11.0
11.5
Validate
Solution:
Sixth observations = (Sum of last 6 observations + Sum of first 6 observations) – Sum of 11 observations
=
(
6
×
11.5
+
6
×
10.5
)
−
11
×
11
=
(
69
+
63
)
−
121
=
11
© examsnet.com
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