Lesson: Addition: Decimals Column-Addition
SWBAT add whole numbers with decimals using column addition.
Materials Needed: DN Worksheet, white board, dry erase markers, graph paper, and Example Chart Decimal Addition, and IND Worksheet.
Vocabulary: column-addition method, place value, ones, tens, hundreds, and thousands.
Do Now (5 min): The teacher passes out half a sheet of graph paper to each student. On the board or chart the teacher writes the following:
Add 78,901 + 23,799 using column-addition method
Subtract 86,372 – 67,184 using trade-first method
Add 65,095 + 78,429 using column-addition method
Subtract 90,278 – 34,889 using the trade-first method
Opening (3- 5 min): Teacher quickly reviews answers to the Do Now and then says, “Today, we are going to review addition. We will be learning about adding numbers with decimals. By the end of this lesson, you will be able to add whole numbers with decimals using column addition.”
Direct Instruction (10 min): The teacher will be teaching column-addition with decimals to the students. The steps are as follows.
1. Rewrite the problem so the decimals are aligned. Fill in zeros to hold places.
2. Add the numbers in each column. Write each sum in its column
3. If there are 2 digits in the 1s place, trade 10 ones for 1 ten.
4. If there are 2 digits in the 10s place, trade 10 tens for 1 hundred.
5. If there are 2 digits in the 100s place, trade 10 hundreds for 1 thousand.
6. If there are 2 digits in the 1000s place, trade 10 thousands for 1 ten thousand.
7. Bring down the decimal so it is in the answer!
The teacher should model at least one problem for the students. See Example Chart Decimal Addition. The teacher should point out the place value of each column as he/she completes the addition for that column. The teacher should model the first example problem and 1 – 2 more problems.
Guided Practice (10 min): The teacher puts up the Guided Practice chart (See Example Chart Decimal Addition) and the students use graph paper to complete the problems while the teacher circulates to assist.
Independent Practice (10 min): The students should be given the IND Worksheet. The students should complete it individually and turn it in.
Closing (2-3 min): Teacher calls the attention of the students back toward the front of the class to ask what they learned about.
|IND add decimal Classwork||
|Example Chart Decimal Addition Exemplar||