What is the difference between 0.3 and3?

0.3 is the same as 3 tenths of one (1.0) This can be written as 3 /10 or 3 over ten

Whereas 3.0 is equal to 30/10

Or

If you want the mathematical answer 3/10 +7/10 + 2.0 equals 3.0

the difference between 0.3 + 3.0 equals 2.7