Three spheres of equal size are composed of aluminum (density $=2.70 \mathrm{~g} / \mathrm{cm}^{3}$ ), silver (density $\left.=10.49 \mathrm{~g} / \mathrm{cm}^{3}\right)$ and nickel (density $\left.=8.90 \mathrm{~g} / \mathrm{cm}^{3}\right)$. List the spheres from lightest to heaviest.