In this lesson we are going to look at adding and subtracting decimals. Here's our first example: 4.25 plus 1.967. Or we can read it as four and 25 hundredths plus one and 967 thousandths. Now to set this up, the first thing that we want to do is line up the decimal points of each number so that they're right on top of each other. So here's what it will look like. Notice that the decimal points are right above each other. The next thing that we want to do is make sure that both numbers end at the same place value. Our first number, the four and twenty-five hundredths ends with the hundredths place value where that five is. Our other number ends with the seven in the thousandths place. We want to make sure both numbers go out to the same place value. So we can add zeros at the end of any number that we need to to fill in any missing pieces. So we can put a zero after that five. So that now that number goes out to the thousandths place as well. Now we can go ahead and add the numbers as we would normally add any numbers. The zero plus seven gives us seven. Five plus six gives us eleven. Drop down the one, carry the other one. One plus two plus nine gives us twelve. Drop the two, carry the one. One plus four plus one gives us six. And now our very last step is to place that decimal point in the answer. Very easy to forget to do that. So make sure that you always put your decimal point in your answers, your last step. And since we have the decimal points lined up in the numbers that we were adding, we just drag that decimal point down into our answer and everything is all set. Our final sum is six and 217 thousandths. In this next example we have a whole number, 19 minus a decimal five and 83 hundredths. Now we said that our first step is to line up the decimal points. Well the number 19 does not have a decimal point because it's a whole number. But remember whenever we need a decimal point and a whole number we just place it right at the end. Now we can write our minus 5.83 underneath making sure that the decimal points are lined up right above each other. Now we want to make sure that both numbers go out to the same place value. The second number, 5.83 goes out to the hundredths place where that three is. So we also need to make sure that our 19 goes out to the hundredths place. We can add two zeros at the end to do that. Now we can subtract as normal. Of course we can't really subtract from the zeros there. So we're going to need to borrow from a number that's not a zero to change those zeros into tens. So the first number we come across that’s not a zero is that nine. So we're going to borrow one from that to make it an eight. That can make the zero next to it turn into a ten. Now that very last zero at the end, we can't leave that as a zero either. We need to make that a ten. So that means we need to borrow one from this one, make that into a nine so that our very last zero can become a ten. Okay, so now we're all set up. We're not subtracting from any zeros anymore. We did enough borrowing to make sure we're not subtracting from zero. Now we can go ahead and subtract ten minus three, seven. Nine minus eight, one. Eight minus five gives us three. Bring down the one. And of course, our very last step - don't forget this last step - to place the decimal point in the answer and just drag it down from where the other decimal points are. Our final answer is one and 317 hundredths. All right, so just make sure that you follow these steps whenever you're adding subtracting with decimals. Line up the decimal points. Make sure that both numbers go out to the same place value. Add any extra zeros in the end as you need to. And then from there you're just adding and subtracting as normal and place that final decimal point in the answer so that it lines up with the other decimal points.