Question

Write each decimal number as a percent. $$0.004$$

Short answer

Question: Convert the decimal number 0.004 into a percentage. Answer: $$0.4\%$$

Step-by-step solution

Multiply by 100

Multiply the decimal number by 100: $$0.004 * 100 = 0.4$$

Add the percent symbol

Add the percent symbol to the result from Step 1: $$0.4\%$$ The decimal number 0.004 can be written as $$0.4\%$$.

Key concepts

Percent Conversion

Converting decimals to percents is a fundamental skill that allows individuals to understand proportions and comparisons in daily life as well as in various academic fields. To convert a decimal to a percent, you simply multiply the decimal number by 100. This is because 'percent' means 'per hundred', so you are converting a fraction (the decimal) to how many out of a hundred, which is what a percentage represents.

For example, with the decimal 0.004, you multiply by 100 to get the number that represents the decimal as parts out of a hundred. The multiplication step looks like this: \(0.004 \times 100 = 0.4\). After multiplying, you have a number that is the direct equivalent to the decimal in terms of percent. This basic procedure turns any decimal into a percentage, allowing for a clear visual representation of small numbers or ratios, which is especially useful in statistics or finance.

Percent Symbol

Once you have converted a decimal to a percent, it is crucial to add the percent symbol (%) afterward. The symbol serves as an indicator that the number is now read as a percentage of 100, not as a plain decimal or fraction. This percent symbol is universally recognized and allows anyone reading a number to understand that it is a part of a whole, divided into 100 equal parts.

In our example of converting 0.004 to a percent, we found that the multiplication gave us 0.4. Without the percent symbol, 0.4 could be interpreted as a plain decimal, but attaching the symbol, as in \(0.4\text{%}\), clarifies that it stands for 0.4 parts out of 100 parts – a very small portion indeed. Therefore, never omit the percent symbol after converting from a decimal to a percentage; it's the essential final touch that conveys the correct meaning.

Multiplying Decimals

Multiplying decimals is an operation that underpins the process of converting decimals to percents. When multiplying a decimal by 100, the aim is to shift the decimal point two places to the right, which effectively converts the decimal value into a percentage.

It’s important to remember that when you move the decimal point, you may not always end up with a whole number. In cases where the decimal is very small, such as 0.004, multiplying by 100 will not dramatically increase the size of the number. Instead, you get 0.4, which may initially give the impression of being an insignificant change, but correctly represents the proportion when converted to a percentage.

When teaching multiplication of decimals, ensure that students are comfortable with the concept of place value, as understanding this is critical to multiplying decimals accurately. By practicing this skill, students will be able to handle a variety of mathematical problems beyond just percent conversions more confidently.