How do you add using numbers in standard form?

Say we have two numbers in standard form, 3x10^8 and 4x10^7. You need to get the numbers so that the part indicating the number of zeros to add on is the same, i.e. in this case we could change 3x10^8 into 30x10^7 (think of it by taking out one of the x10 from the 10^8, as 30x10^7=3x10x10^7=3x10^8). This is so that we know we can just add the first part together now as these numbers are of the same form. We would therefore get 34x10^7, or 3.4x10^8.