Question

The arithmetic mean of $6$ numbers is $15$. On adding $7th$ number the mean becomes $14$. Find the $7th$ number.

Answer 1

AM of 6 numbers is $15$

Let $7th$ number is $x$

Total sum of $6$ number $=15\times 6$

$=90$

$\Rightarrow \frac{90+x}{7}=14$

$90+x=98$

$\Rightarrow x=8$

Hence, the answer is $8.$