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Question : 82 of 100

Marks: +1, -0

Solution:

Let the unknown number be x.

Then

\frac{\sum\limits_{i=1}^{5} X_i}{5} = \overline{X} = 30

\sum\limits_{i=1}^{5} X_i = 150

\sum\limits_{i=1}^{4} X_i + X = 150

\sum\limits_{i=1}^{4} X_i = 150 - X

\frac{\sum\limits_{i=1}^{4} X_i}{4} = \frac{150 - x}{4}

But it is given that,

\frac{\sum\limits_{i=1}^{4} X_i}{4} = 28

Hence substituting above data in the equation, we get

\frac{\sum\limits_{i=1}^{5} X_i}{4} = 28

\therefore \frac{150 - X}{4} = 28

150 - x = 4(28)

150 - x = 112

x = 150 - 112

x = 38

The Unknown number is 38

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