# NCERT Class 11 Mathematics Solutions: Chapter 15 –Statics Miscellaneous Exercise Part 1

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1. The mean and variance of eight observations are , respectively. If six of the observations are , find the remaining two observations.

Answer:

Consider the remaining two observations be .

So, the observations are .

Mean,

……………………………….. eq (1)

……………..[Using (1)]

…………………eq (2)

From eq (1)

………….. eq (3)

From eq (2) and (3),

…………..eq (4)

Subtracting eq (4) from (2),

………………………….. eq (5)

So, from (1) and (5),

,

When

,

When

The remaining observations are .