Question

Tolong di jawab ya kak !!
1+2+3+4+...+119 =

Answer 1

1/2n x [2a+ (n-1)b]
1/2 x 119 x [ 2 x 1 + ( 119-1) 1]
59,5 x [2 + (118) 1 ]
59,5 x 120
= 7140