tolong jawabkan no 18,19, dan 20

18.
R^2 = 17^2 - 15^2 = 289 - 225 = 64
R = 8

R = r1 - r2
8 = r1 - 3
r1 = 11

Jawab C

19.
CD^2 = 26^2 - 10^2 = 676 - 100 = 576
CD = 24

Luas
= 1/2 (18 + 8) × 24
= 312

Jawab A

20.
Lingkaran besar
= 210/360 × 22/7 × 14 × 2
= 7/12 × 88
= 154/3

Lingkaran kecil
= 150/360 × 22/7 × 7 × 2
= 5/12 × 44
= 55/3

Total tali
= 154/3 + 55/3 + 2L
= 209/3 + 2L

Jawab C