Question

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

Answer 1

$\Rightarrow$ It is given that Mean of $5$ observations is $15.$

$\therefore$ The sum of observations $=15\times 5=75.$

$\therefore$ It is given that mean of the first $3$ observations is $14.$

$\therefore$ The sum of first three observations $=14\times 3=42.$

$\Rightarrow$ Given that mean of the last $3$ observations is $17.$

$\therefore$ The sum of the last three observations $=17\times 3=51$

$\therefore$ The third observation $=(42+51)-75$

$=93-75$

$=18$