Question: User: 0.004 as a percentage
1. **State the problem:** Convert the decimal number $0.004$ to a percentage.
2. **Formula used:** To convert a decimal to a percentage, multiply the decimal by 100 and add the percentage symbol (%).
3. **Calculation:**
$$0.004 \times 100 = 0.4$$
4. **Interpretation:** Multiplying by 100 shifts the decimal point two places to the right, converting the decimal to a percentage.
5. **Final answer:**
$0.004$ as a percentage is $0.4\%$.