Skill: Find common factors

A common factor is a whole number that divides evenly into two numbers.

To find common factors:

1. List the factor pairs for the first number.
2. List the factor pairs for the second number.
3. Find the numbers that appear in both lists.

Example: Find the common factors of $18$ and $24$.

Step 1: List the factor pairs of $18$.

$$1 \times 18=18$$ $$2 \times 9=18$$ $$3 \times 6=18$$

So, the factors of $18$ are:

$$1,\ 2,\ 3,\ 6,\ 9,\ 18$$

Step 2: List the factor pairs of $24$.

$$1 \times 24=24$$ $$2 \times 12=24$$ $$3 \times 8=24$$ $$4 \times 6=24$$

So, the factors of $24$ are:

$$1,\ 2,\ 3,\ 4,\ 6,\ 8,\ 12,\ 24$$

Step 3: Find the factors in both lists.

The numbers that appear in both lists are:

$$\boxed{1,\ 2,\ 3,\ 6}$$

Therefore, the common factors of $18$ and $24$ are $\boxed{1, 2, 3, \text{ and } 6}$. Each one divides both numbers evenly, with no remainder.