One grain of sand weighs 0.0006g. how many grains in 7200kg

Firstly we need to convert 7200 kg to g. So it will be 7200kg x 1000g which is 7200000 g. 

Now we have 0.0006 g and 7200000 g. To see how many grains are in 7200000 g , we divide 7200000 by 0.0006 g

so 7200000/0.0006 = 12000000000 ( 9 zeros)

Therefore, there are 12000000000 grains of sand in 7200 kg