Question

Jumlah bilangan kelipatan 3 antara 400 sampai 500

Answer 1

A = 402
b = 3
U terakhir = 498

Un = a+(n-1)b
498 = 402 +(n-1)3
498 = 402 + 3n - 3
498 = 399 + 3n
3n = 498 - 399
3n = 99
n = 99/3
n = 33

Sn = n/2(a+Un)
S33 = 33/2 (402+498)
S33 = 16,5 x 900
S33 = 14850