We can do addition, subtraction, multiplication, and even division with decimals. That's a lot to think about all at once. We'll start by just looking at adding and subtracting decimal numbers. For addition and subtraction, there are three steps to follow.
Let's use this example:
9.4 + 51.27 + .403
Notice how the equation above is written. First, rewrite the equation in columns so we can line up the decimal points.
The decimal numbers have different places. The number with the most digits is .403. It ends in the thousandths place. The other numbers don't have a digit in the thousandths place. Fill out the other decimal numbers with zeros, up to the thousandths. This will square out the decimal places for all the numbers.
Next, write the decimal point for the answer. Remember, this decimal point is lined up with all the others.
Adding zeros to the end of a decimal number doesn't change its value. For example, 9.400 and 9.4 have the same value. So, how does adding zeros help us in adding or subtracting decimals? To see its effect, let's try solving the problem:
For the thousandths place, we have 0 + 0 + 3 = 3. It's less confusing this way because none of the numbers in the equation are left out in the solution.
We add up the hundredths, the tenths, and then the ones and tens in this way, too.
Finally, we have our answer: sixty-one and seventy-three thousandths (61.073).
We can do the same for subtraction. Squaring out the decimal numbers with zeros will help us a lot when we start solving subtraction problems.
