Tentukan jumlah bilangan ganjil antara 200 sampai 300

201,203,205,207,209,211,213,215,217,219,dst

a = 201
b = 2

Un = 299
a + (n -1) b = 299
201 + (n - 1) 2 = 299
201 + 2n - 2 =299
199 + 2n = 299
2n = 100
n = 50

Sn = n/2 (2a + (n -1) b)
S50 = 50/2 (2 . 201 + 49 . 2)
= 25 (402 + 98)
= 25 ( 500)
= 12.500