CTET 2 Math and Science Feb 2016 Paper

Question : 36 of 120

Marks: +1, -0

The mean of the five observations x, x + 2, x + 4, x + 6, x + 8 is 11. Then, the mean of the first three observations is

Solution:

According to the question

\;\;{x+x+2+x+4+x+6+x+8}/{5}=11

⇒5x+20=55

⇒5x=55-20=35

∴x=35/5=7

Mean of first three observations

=\;\;{x+x+2+x+4}/{3}=\;\;{3x+6}/{3}

=\;\;{3×7+6}/{3}=\;\;{27}/{3}=9

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