To work out standard form, you must count the amount of numbers the decimal point must jump to get a number which is less than 10.
As an example, the number 120 would be 1.2x10^2
This is because 120 can also be written as 120.0, and to make the number smaller than 10 (1.2) the decimal point has to move 2 places to the left making it x10^2.
a) There are 1000g in a Kg, meaning there are 7200000g there. In standard form, it has to be a decimal x10 to a power. 7200000 becomes 7.2x10^6
b) 0.0006 will be 6.0x10^-4
c) 7200000/0.0006=12000000000 which in standard form is 1.2x10^10
