Math Core

Some facts are extra easy to remember. When you add a number to itself, you get a double. Doubles can help you with other facts too!

Doubles

A double is two groups that are the same size.

🐞🐞🐞🐞 + 🐞🐞🐞🐞

That is $4 + 4 = 8$ .

Definition

Double

A double is a fact where you add a number to itself, like $6 + 6$ .

Learn these doubles:

Double	Sum
$1 + 1$	2
$2 + 2$	4
$3 + 3$	6
$4 + 4$	8
$5 + 5$	10
$6 + 6$	12
$7 + 7$	14
$8 + 8$	16
$9 + 9$	18
$10 + 10$	20

Near doubles

What is $6 + 7$ ? It is almost $6 + 6$ . The 7 is just 1 more than 6.

$6 + 6 = 12$ . Then add 1 more: 13.

So $6 + 7 = 13$ . This is called a near double.

Near doubles

When two numbers are next to each other, like 6 and 7, use the double of the smaller number. Then add 1.

Worked example: A double

What is $7 + 7$ ?

This is a double. $7 + 7 = 14$ .

Worked example: A near double

What is $8 + 9$ ?

9 is 1 more than 8. Think $8 + 8 = 16$ . Add 1 more: 17.

$8 + 9 = 17$ .

Worked example: Order doesn't matter

What is $5 + 4$ ?

4 is the smaller number. Think $4 + 4 = 8$ . Add 1 more: 9.

$5 + 4 = 9$ .

Common mistake

Use the double of the smaller number, then add 1. For $6 + 7$ , think $6 + 6$ , then add 1. If you use $7 + 7$ , you must take 1 away instead.

Practice

Practice 1

What is $7 + 7$ ?

Type a number.

Practice 2

What is $9 + 9$ ?

Type a number.

Practice 3

Six ducks swim in a pond. Six more ducks join them. How many ducks are there now?

Type a number.

Practice 4

What is $5 + 6$ ?

Type a number.

Practice 5

Which double helps you find $7 + 8$ ?

Practice 6

What is $8 + 7$ ?

Type a number.

Practice 7

What is $10 + 9$ ?

Type a number.