Add three numbers – use doubles

Key notes:-

  1. What Are Doubles?
    Doubles refer to adding the same number to itself. For example:
  • 2 + 2 = 4
  • 5 + 5 = 10

2. Using Doubles to Add Three Numbers
When adding three numbers, students can look for doubles to make the addition easier. For example:

  • 4 + 4 + 2
    Step 1: Identify the double (4 + 4 = 8)
    Step 2: Add the remaining number (8 + 2 = 10)

3. Strategy

  • Encourage students to group the numbers so they can spot a pair of numbers that are the same (doubles).
  • Once they add the double, they simply need to add the third number to the result.

4. Examples:

  • 3 + 3 + 5
    Step 1: Identify the double (3 + 3 = 6)
    Step 2: Add the remaining number (6 + 5 = 11)
  • 7 + 7 + 1
    Step 1: Identify the double (7 + 7 = 14)
    Step 2: Add the remaining number (14 + 1 = 15)

Learn with an example

✒️Add: 1 + 3 + 3 =

Hint: Start by adding a double.

First, add the doubles 3 and 3 to make 6:

1 + 3 + 3 = ?

1 + 6 = ?

Now add 1 and 6:

1 + 6 = 7

The sum is 7.

✒️Add: 5 + 2 + 2 =

Hint: Start by adding a double.

First, add the doubles 2 and 2 to make 4:

5 + 2 + 2 = ?

5 + 4 = ?

Now add 5 and 4:

5 + 4 = 9

The sum is 9.

✒️Add: 1 + 1 + 2 =

Hint: Start by adding a double.

First, add the doubles 1 and 1 to make 2:

1 + 1 + 2 = ?

2 + 2 = ?

Now add 2 and 2:

2 + 2 = 4

The sum is 4.

Let’s practice!