Q2 of 8 Page 293

The mean of 5 observation is 15. If the mean of the first three observations is 14 and that of the last three is 17. Find the third observation.


Mean of 5 observations = 15


Sum of all observation = 15× 5


Mean of first three observations = 14


Sum of 3 observations = 14×3


Mean of last three observations = 17


Sum of last three observations = 17×3


Let the 3rd observation be the x


So, according to the question,


Sum of all observation = sum of 1st three observations + sum of last three observations – 3rd observation


15 × 5 = 14 × 3 + 17 × 3 – x


x = 42 + 51 – 75


x = 18


The Third Observation is 18.


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1

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 3

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