Adding Decimals

1. Adding Decimals 5.NBT.B.7

2. Adding Decimals 0.37 0.37 + 0.21 0.21 + 0 . 5 8 Here is 0.37 + 0.21. First, let’s copy the decimals below. So, the sum is 0.58. … so that the decimal points are lined up … Now, we are ready to add. Let’s begin in the hundredths place – what is 7 + 1? What is 0 + 0? What is 3 tenths + 2 tenths? 5 tenths Here is the decimal point. Let’s mark it below. 8 0 … and the ones places are lined up. Then let’s align the decimals carefully …

3. Adding Decimals 6.48 6.48 + 2.31 2.31 + 8 . 7 9 Here is 6.48 + 2.31. First, let’s copy the decimals below. Then let’s align the decimals carefully … … so that the decimal points are lined up … Now, we are ready to add. 9 It’s 8. 7 tenths Here is the decimal point. Let’s mark it below. What is 6 + 2? What is 4 tenths + 3 tenths? So, the sum is 8.79. Let’s begin in the hundredths place – what is 8 + 1? … and the ones places are lined up.

4. Adding Decimals 23.4 23.4 + 5.25 5.25 + 2 8 . 6 5 6 tenths Let’s begin in the hundredths place. There is only one digit, which is a 5. Let’s mark it below. What is 3 + 5? 8 So, the sum is 28.65. … and the ones places are lined up. First, let’s copy the decimals below. … so that the decimal points are lined up … Then let’s align the decimals carefully … And here are 2 tens ... … which we can mark below. Now, we are ready to add. Here is 23.4 + 5.25. What is 4 tenths + 2 tenths? Let’s mark it below. Here is the decimal point.

5. Adding Decimals 52.318 + 6.4 52.318 6.4 + 5 8 . 7 1 8 In the hundredths place, there is a 1. Now, we are ready to add. Here is the decimal point. Let’s mark it below. What is 2 + 6? 8 So, the sum is 58.718. … so that the decimal points are lined up … What is 3 tenths + 4 tenths? Here are 5 tens ... … which we can mark below. Now let’s write the second decimal … Let’s write the first decimal below. Here is 52.318 + 6.4. … and the ones places are lined up. 7 tenths Let’s mark it below. Let’s begin in the thousandths place. There is only one digit, which is an 8. Let’s mark it below.

6. Adding Decimals 73.83 + 24 73.83 24 + 9 7 . 8 3 Here is 73.83 + 24. Let’s write the first number below. Notice that 24 is not a decimal, so there are no decimal points to line up. Instead, we will write the number here … … so that the ones places are lined up. Now, we are ready to add. In the hundredths place, there is a 3. And what is 7 + 2? Let’s mark it below. Let’s mark it below. 7 So, the sum is 97.83. What is 3 + 4? 9 In the tenths place, there is an 8. Let’s mark it below. Here is the decimal point.

7. Adding Decimals 1.48 + 36.925 1 1 1.48 36.925 + 3 8 . 4 0 5 Here is the decimal point. Let’s mark it below. What is 1 + 1 + 6? … so that it still says 14. So, the sum is 38.405. 5 How many thousandths are there? Here are 3 tens ... … which we can mark below. Now, we are ready to add. … and the ones places are lined up. … and regroup the 1 … In the tenths place, what is 1 + 4 + 9? 14 Let’s write the decimals below … Here is 1.48 + 36.925. To show 10, let’s mark the 0 … How many hundredths? … so that it still says 10. To show 14, let’s mark the 4 … … and regroup the 1 … 10 … so that the decimal points are lined up … 8

8. Adding Decimals Closing Question

9. Adding Decimals 3.491 + 24.87 1 1 3.491 24.87 + 2 8 . 3 6 1 Here is the decimal point. Let’s mark it below. What is 1 + 3 + 4? … so that it still says 13. So, the sum is 28.361. 1 How many thousandths are there? Here are 2 tens ... … which we can mark below. Now, we are ready to add. … and the ones places are lined up. … and regroup the 1 … In the tenths place, what is 1 + 4 + 8? 13 Let’s write the decimals below … Here is 3.491 + 24.87. To show 16, let’s mark the 6 … How many hundredths? … so that it still says 16. To show 13, let’s mark the 3 … … and regroup the 1 … 16 … so that the decimal points are lined up … 8