Answer:
Adding, Write down the numbers, one under the other, with the decimal points lined up; Put in zeros so the numbers have the same length (see below for why that is OK) Then add using column addition, remembering to put the decimal point in the answer
Subtracting, Write down the two numbers, one under the other, with the decimal points lined up.
Add zeros so the numbers have the same length.
Then subtract normally, remembering to put the decimal point in the answer.
Explanation: