Square kilometer

\[\begin{aligned} y[cm^2] &= 1\times 10^{10}x[km^2] \\ y[m^2] &= 1000000x \\ y[inch^2] &= 1.55\times 10^9x \\ y[ft^2] &= 1.07639\times 10^7x \\ y[yd^2] &= 1195990x \end{aligned}\]