2 + 3 + 4 + 5 +. + 48 + 49 + 50 = how to find the law,

2 + 3 + 4 + 5 +. + 48 + 49 + 50 = how to find the law,

(2 + 50) times 49 divided by 2
(first + last) number of multiplications divided by two