Hitung jumlah bilangan kelipatan 4 antara 100 dan 200

Un = a + (n-1) b
200= 100 + (n-1) 4
200 = 100 + 4n - 4
4n = 200-196
n= 4/4 = 1

Sn = 1/2 (100+200)
= 300:2
= 150

Bab Barisan dan Deret
Matematika SMP Kelas IX

104, 108, ....., 196
a = 104
b = 4
Un= 196

Un = a + (n - 1) b = 196
104 + (n - 1) x 4 = 196
(n - 1) x 4 = 196 - 104
n - 1 = 92 / 4
n = 23 + 1
n = 24

Sn = n/2 x (a + Un)
S24 = (24/2) x (4 + 196)
S24 = 12 x 200
S24 = 2.400