Answer
Find the mass in grams.
$$\frac{700,000,000,000 dollars}{(28.40 dollars)/gram} = 2.47 \times 10^{10} grams$$
Find the volume of this gold.
$$\frac{2.47 \times 10^{10} grams}{19.3 g/cm^{3}} = 1.28 \times 10^{9} cm^{3}$$
Find the length of the side of a cube with this volume.
$$L = \sqrt[3]{1.28 \times 10^{9} cm^{3}} = 1085 cm$$
