Skill: Write ratios using colon notation

A ratio compares two quantities. To write a ratio in colon notation:

1. Identify the first quantity.
2. Identify the second quantity.
3. Write their amounts in the same order with a colon between them:

$$\text{first amount}:\text{second amount}$$

Example: A basket has 6 apples and 4 oranges. Write the ratio of apples to oranges.

• First quantity: apples, so write $6$ first.
• Second quantity: oranges, so write $4$ second.
• Separate the numbers with a colon:

$$6:4$$

So, the ratio of apples to oranges is $\boxed{6:4}$.

The order matters. The ratio of oranges to apples would be $4:6$, which is a different comparison. A ratio such as $6:4$ represents the same comparison as $\frac{6}{4}$, but colon notation writes the comparison with a colon.