AMC 8 1990 Problem 15

The area of this figure is $100\text{ cm}^2$. Its perimeter is

[figure consists of four identical squares] $\text{(A)}\ \text{20 cm} \text{(B)}\ \text{25 cm} \text{(C)}\ \text{30 cm} \text{(D)}\ \text{40 cm} \text{(E)}\ \text{50 cm}$