We'll solve both questions using conversion factors, making sure that the units cancel our correctly:
PART A
We'll convert kilograms into grams, as following:
[tex]6300kg\cdot\frac{1000g}{1kg}\rightarrow6.3\times10^6g[/tex]
PART B
We'll convert grams of sand into grains of sand.
[tex]6.3\times10^6g\cdot\frac{1\text{ grain}}{7\times10^{-5}g}\rightarrow9\times10^{10}\text{ grains}[/tex]
