Recognize odd and even quantities informally

A quantity within the familiar counting range through 20 is even when its objects can be organized into pairs with none left over, and odd when pairing leaves exactly one object; the same distinction applies to its numeral and to representations such as dot arrangements or ten-frames. This understanding connects even quantities with sums of two equal addends and supports later work with counting patterns and multiplication, without requiring formal divisibility rules or generalization to unrestricted larger numbers.

Detailed Explanation: Recognize odd and even quantities informally

To tell whether a quantity is even or odd, make pairs of its objects.

If every object has a partner, the quantity is even.
If exactly one object is left without a partner, the quantity is odd.

Example: Is $8$ even or odd?

Step 1: Count the objects.

There are $8$ dots:

● ●   ● ●   ● ●   ● ●

Step 2: Look for pairs.

The dots make $4$ pairs:

pair 1: ● ●
pair 2: ● ●
pair 3: ● ●
pair 4: ● ●

Step 3: Check for leftovers.

No dots are left over. Every dot has a partner.

So, $8$ is even.

We can also show this with equal groups:

8=4+4

The numeral $8$ represents an even quantity because its objects can be organized into pairs with none left over.

Learn by doing: Recognize odd and even quantities informally

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Number Sense - Even or Odd

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