Question

Out of $250$ observations, the first $100$ observations have mean $5$ and the average of the remaining $150$ observations is $25/3$. What is the average of the whole group of observations?

• A. $6$
• B. $7$
• C. $8$
• D. $9$

Answer 1

The correct option is B $7$

Solution:

There are total 250 observations

Mean i.e. average of 100 observations

$=5$

Average of reaming 150 observations

$=\frac{25}{3}$

$\therefore$ Average of 250 observations

$=\frac{100\times 5+150\times \frac{25}{3}}{250}$

$=\frac{100\ast 5+50\times 25}{250}$

$=\frac{500+1250}{250}$

$=\frac{1750}{250}$

$=7$

Average means each object is having

appropriate that value