How to Add Decimals
Adding decimals is almost as easy as adding whole numbers. As long as you set up the problem correctly, you’re in good shape. To add decimals, follow these steps:

Line up the decimal points.

Add as usual from right to left, column by column.

Place the decimal point in the answer in line with the other decimal points in the problem.
For example, suppose you want to add the numbers 14.5 and 1.89. Line up the decimal points neatly as follows:
Begin adding from the righthand column. Treat the blank space after 14.5 as a 0 — you can write this in as a trailing zero. Adding this column gives you 0 + 9 = 9:
Continuing to the left, 5 + 8 = 13, so put down the 3 and carry the 1:
Complete the problem column by column, and at the end, put the decimal point directly below the others in the problem:
When adding more than one decimal, the same rules apply. For example, suppose you want to add 15.1 + 0.005 + 800 + 1.2345. The most important idea is lining up the decimal points correctly:
To avoid mistakes, be especially neat when adding a lot of decimals.
Because the number 800 isn’t a decimal, you can place a decimal point and a 0 at the end of it to be clear about how to line it up. If you like, you can make sure all numbers have the same number of decimal places (in this case, four) by adding trailing zeros. After you properly set up the problem, the addition is no more difficult than in any other addition problem: