1. Jumlah bilangan kelipatan 3 antara 100 dan 300 adalah... 2. Perbandingan panjang dan lebar persegi panjang 7 : 4. Jika keliling persegi panjang tersebut 66 c

1) 102 + 105 + 108 + ... + 297
a = 102
b = 3

Un = a + (n - 1)b
297 = 102 + (n - 1)3
3n - 3 = 297 - 102
3n = 195 + 3
n = 198/3
n = 66

Sn = n/2 (a + Un)
S66 = 66/2 (102 + 297)
S66 = 33(399)
S66 = 13.167

2) p : l = 7 : 4
Kita misalkan
p = 7x
l = 4x

K = 2(p + l)
66 = 2(7x + 4x)
11x = 66/2
x = 33/11
x = 3

p = 7x
p = 7(3)
p = 21 cm

l = 4x
l = 4(3)
l = 12 cm

L = p × l
L = 21 × 12
L = 252 cm^2