Answer:
640 cm²
Explanation:
The ratio between the area two similar polygon are the ratio between their sides squared.
Given side S₁ and side S₂, you can find the area of the second shape by multiplying the area of the first shape by a factor of (S₂/S₁)².
This might sound confusing if you're not used to hearing math terms so lets solve it in this problem.
The side of the first trapezoid is 5cm, so S₁ = 5
The side of the second trapezoid is 20cm so S₂ = 20.
The ratio between them is 20/5=4
To find the area of the second shape, we just have to multiply the area of the first one by the ratio², ie. (S₂/S₁)².
40(4)² = 40(16) = 640 cm²