Jumlah semua bilagan genap antara 50 dan 90 adalah…. a. 1330 c.1360 d.1930 d.1960

a = 52

Un = 88

Un = a+(n-1)b

88 = 52+(n-1)2

36 = (n-1)2

n-1 = 18

n = 18+1

n = 19

Sn = n/2×(a+un)

= 19/2 × (52+88)

= 19/2 × 140

= 19× 70

= 1330 (a)