# How do you find the sum of the series 1 from i=1 to 42?

Oct 16, 2016

$1 + 2 + 3 + \ldots + n = {\sum}_{i = 1}^{i = n} i = \frac{n \cdot \left(n + 1\right)}{2}$
$1 + 2 + 3 + \ldots + 42 = {\sum}_{i = 1}^{i = 42} i = \frac{42 \cdot \left(42 + 1\right)}{2} = 21 \cdot 43 = 903$