Solution:
we are given that one grain of sand weighs 7x10^-5 Kg.
There is a total of 6300Kg of sand.
So we will divide the total weight by weight of one grain of sand.
Number of sand [tex]=\frac{6300}{7\times10^{-5}}[/tex]
Number of sand [tex]=\frac{6300\times10^{5}}{7}[/tex]
Number of sand [tex]=900\times10^{5}[/tex]
Hence there are 900x10^5 sands.