Question

Jumlah bilangan kelipatan 3 antara 400 sampai 500 adalah....

Answer 1

A = 402
un = 498
b = 3

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 = 1/2 n (2a + (n-1)b)
= 1/2 . 33 (2.402 + (33-1)3)
= 1/2 . 33 (804 + (32)(3))
= 1/2 . 33 (804 + 96)
= 1/2 . 33 (900)
= 450 . 33
= 14850