# Math Help - A sum on arithmetic mean...

1. ## A sum on arithmetic mean...

The mean of 5 numbers is 18. If one number is excluded, their mean is 16. Find the excluded number.

2. $\frac{x_1+x_2+x_3+x_4+x_5}{5} = 18\implies x_1+x_2+x_3+x_4+x_5 = 90$

$\frac{x_1+x_2+x_3+x_4}{4} = 16\implies x_1+x_2+x_3+x_4 = 64$

$
x_5=90-64
$