Question

Jumlah bilangan kelipatan 3 antara 100 dan 300?

Answer 1

Kelipatan 3 berarti b = 3
a = 102
Un = 297

Un = a + (n-1)b
297 = 102 + (n-1)3
297-102 = 3(n-1)
195 = 3(n-1)
n-1 = 195/3
n-1 = 65
n = 66

Sn = n/2 (a+Un)
     = 66/2 (102+297)
     = 33 (399)
     = 13167