Add Decimals

We can use models to add decimals

Steps to follow to add two decimals (1.50 + 1.35):
Step 1: Model 1.50 and 1.35
Show 1.50 by coloring one whole grid red and coloring 50/100 of the second grid red.
Show 1.35 by coloring one whole grid blue and coloring 35/100 of the second grid blue.

Step 2: Put 1.50 and 1.35 together and count the total number of shaded squares
Total number of shaded squares = 100 + 100 + 85
100 squares = 1; 85 squares = 0.85
1.50 + 1.35 = 2.85

To add two decimals, both the decimals should have the same number of decimal places. We can attach 0s to the end of the decimals.

5.5 + 1.62 = 5.50 + 1.62

Steps to follow to add decimals (2.22 + 1.15):

 Step 1: Line up the decimal points

  2.22
+1.15

Step 2: Add each place. Regroup if needed. Write the decimal point in the sum

  2.22
+1.15
  3.37

Steps to follow to add two decimals using the Partial-Sums Method (4.12 + 6.50):
Step 1: Add the 1s
4 + 6 = 10

Step 2: Add the 0.1s
0.1 + 0.5 = 0.6

Step 3: Add the 0.01s
0.02 + 0.00 = 0.02

Step 4: Add the partial sums
10 + 0.6 + 0.02 = 10.62

Steps to follow to add two decimals using Column-Addition Method:
Step 1: Draw lines to separate the 1s, 0.1s, and 0.01s places
Step 2: Add the numbers in each column. Write each sum in its column
Step 3: If there are 2 digits in the 0.01s place, trade 10 hundredths for 1 tenth
Step 4: If there are 2 digits in the 0.1s place, trade 10 tenths for 1 one