1+2+3.............+50=

1+2+3+.....+50 = ?

Sn = 1/2 n (a + Un)
S₅₀ = 1/2 . 50 (1 + 50)
      = 25 x 51
      = 1.275

Bab Bilangan Bulat
Matematika SD Kelas V

penjumlahan bilangan asli berurutan = 1/2 x n x (n +1)
n = 50
1 + 2 + 3 + .. + 50
 = 1/2 x 50 x (50 + 1)
= 25 x 51
= 1.275