# NCERT Class 11 Mathematics Solutions: Chapter 15 –Statics Miscellaneous Exercise Part 2

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1. The mean and variance of observations are , respectively. If five of the observations are . Find the remaining two observations.

Consider the remaining two observations be .

The observations are .

Mean,

Since,

……………………..eq (1)

Variance,

…….[Using(1)

…………….eq (2)

From Eq (1)

……….(3)

From eq (2) and (3)

Subtracting eq (4) from (2),

…………………..eq (5)

So, from eq (1) and (5)

When

When

The remaining observations are .