You would have to multiply 120 x 20 then divide by 8. I hope that helps you!
Answer:
126.4 cm
Step-by-step explanation:
1. 15.8 * 3 = 47.4 (This is the length)
2. Find half of the rectangle
47.4 + 15.8 (width) = 63.2
3. Find the whole perimeter
63.2 * 2 = 126.4