Lesson 1.2 · Addition and Subtraction Facts
Even and odd numbers
Can every kid in a group have a partner? It depends on the number! Some numbers split into pairs with none left over. Others always have one left.
Make pairs
Put the objects in pairs. Look for one left over.
8 socks: 🧦🧦 🧦🧦 🧦🧦 🧦🧦
Every sock has a partner. 8 is even.
7 socks: 🧦🧦 🧦🧦 🧦🧦 🧦
One sock is alone. 7 is odd.
Definition
Even and odd
An even number can be put into pairs with none left over. An odd number always has one left over.
Look at the ones digit
Count by 2s: 2, 4, 6, 8, 10, 12, … These are the even numbers.
Even numbers end in 0, 2, 4, 6 or 8. Odd numbers end in 1, 3, 5, 7 or 9.
Even numbers are doubles
An even number is two equal groups added together.
and .
An odd number can't be split into two equal groups. 9 is . The groups are not equal.
Is it even?
A number is even if you can write it as a double, like . Check the ones digit: 0, 2, 4, 6, 8 means even.
Worked example: Pairs
Is 11 even or odd?
🍪🍪 🍪🍪 🍪🍪 🍪🍪 🍪🍪 🍪
Make pairs. There are 5 pairs and 1 cookie left over. 11 is odd.
Worked example: Write it as a double
Show that 16 is even.
Split 16 into two equal groups: .
It is a double, so 16 is even.
Common mistake
Look at the ones digit only. 18 starts with 1, but it ends in 8. So 18 is even.
Practice
🐟🐟 🐟🐟 🐟🐟
Is the number of fish even or odd?
Is 13 even or odd?
Which number is even?
. Both numbers are the same. What number goes in each box?
Type a number.
Leo has 9 toy cars. He puts them in pairs. How many cars are left over?
Type a number.
List all the even numbers between 11 and 17.
Separate answers with commas, e.g. 2, -5
There are 15 kids in a class. Can every kid have a partner?