For the answer to the question above, volume of 1 sand grain = (0.10 mm)³ = 0.001 mm³
1 mole sand x (6.02214x10^23 grains / mole) x (0.001 mm³ / grain) = 6.02214x10^20 mm³
268,601 mi² x (5280 ft / mi)² x (12 in / ft)² x (2.54 cm / in)² x (10 mm / 1 cm)² = 6.95673x10^17 mm²
V = height x area
height = V / A = 6.02214x10^20 mm³ / 6.95673x10^17 mm² = 865.657 mm
finally...
865.657 mm x (1 cm / 10 mm) x (1 in / 2.54 cm) x (1 ft / 12 in) = 2.84008 ft.
= 6 sig figs.
