tolong jawabkan pakai cara

Rumus : d1 × d2/ 2
1. 28×20/2 = 560/2 = 280 cm²
2. 10×16/2 = 160/2 = 80 cm²
3. 16×22/2 = 352/2 = 176 cm
4. 27×34/2 = 918/2 = 459 cm²
5. 360×2/24 = 720/24 = 30
6. 48×2/16 = 96/16 = 6
7. 150×2/30 = 300/30 = 10
8. 135×2/18 = 270/18 = 15
9. 372×2/31 = 744/31 = 24
10. 592×2/32 = 1184/32 = 37