Odd and Even Numbers
Lessons in this chapter
About Odd and Even Numbers
Odd One Out names a split kids have already half noticed from skip counting by two, and then does something unusual for 2nd grade: it asks them to find a rule that always holds.
Identify Odd and Even Numbers gives the definition that matters: an even number can be split into two equal groups with nothing left over, an odd number cannot. The last-digit shortcut works, but the pairing idea is what explains why it works.
Observe Patterns in Operations with Odd and Even Numbers is the more interesting lesson. Even plus even is always even, odd plus odd is also always even, and odd plus even is always odd. Kids can test these with any numbers they like and find they never fail.
This is the first time a 2nd grader meets a statement that is true for every number rather than for the examples in front of them. Noticing that something always happens, and being able to say why using the pairing idea, is the beginning of mathematical proof.
Identify Odd and Even Numbers and Observe Patterns in Operations with Odd and Even Numbers are two lessons and two worksheets, worked in the page and scored as your child answers. The second is the valuable one: odd plus odd is always even, and noticing why is a 2nd grader's first taste of proof. Both are free.
Frequently asked questions
Identifying a number as odd or even by pairing it up, and then the patterns that follow when you add and subtract them. Two lessons, and the second is where the thinking is. It sits in Operations and Algebraic Thinking (2.OA), which asks 2nd graders to recognize even numbers as two equal groups.
That it can be split into two equal groups with nothing left over. The shortcut is the last digit, 0, 2, 4, 6 or 8, but the pairing idea is what explains the shortcut.
You always get an even number. Each odd number has one left over after pairing, and those two leftovers pair with each other.
Even. It splits into two equal groups of nothing, with nothing left over, and it continues the skip-counting-by-two pattern.
Look only at the last digit. The rest of the number is made of tens, hundreds and so on, all of which are already even.
Because they are a child's first encounter with a rule that holds for every number, not just the ones tested. That is the start of proof.