Question

Write each decimal number as a percent. $$0.09$$

Short answer

Question: Convert the decimal number 0.09 to a percentage. Answer: 9%

Step-by-step solution

Identify the given decimal number

The given decimal number is 0.09.

Multiply the decimal by 100

To convert the decimal to a percentage, we need to multiply it by 100: \[0.09\times100=9\]

Add the percentage symbol

Finally, we add the percentage symbol (%) to the result from Step 2: \[9\%\]

Final Answer

The decimal number 0.09 as a percent is 9%.

Key concepts

Decimal to Percent Conversion

Converting a decimal to a percent is a fundamental skill in mathematics that allows you to express a number as a part of a hundred. Think of it as simply shifting the decimal point two places to the right. Why two places? Because 'percent' means 'per hundred', and moving the decimal point two places to the right effectively multiplies the number by 100. For instance, to convert the decimal 0.09 to a percent:

Multiply the decimal number by 100: \[0.09 \times 100 = 9\]. This action expands the value from parts of one (decimal) to parts of a hundred (percent). Here's a handy tip: one quick way to multiply by 100 is to count two decimal places from the right and place your decimal point there, turning what was once in the hundredths place into the whole number place for percentages. As a real-world example, if 0.09 represented 0.09 parts of a dollar, converting it to a percent tells you that you have 9% of that dollar.

Multiplying Decimals

Multiplying decimals might seem tricky at first, but it's just as straightforward as multiplying whole numbers once you know the ropes. The key is to keep track of the decimal point. First, you can ignore the decimal points and multiply the numbers as if they were whole numbers. Then, you count the total number of decimal places in both of the original numbers combined. This is the number of decimal places the answer must have.

For example, with our earlier conversion problem, you multiply 0.09 by 100. Since 100 is a whole number with no decimal places, you only focus on the decimal places in 0.09, which has two. After multiplying 0.09 by 100 (which gives us 9 as a whole number), we don't need to adjust the decimal place because multiplying by 100, which has zero decimal places, doesn't change the placement.

Percent Symbol

The percent symbol (%) is a widely recognized shorthand in mathematics and everyday life for representing percentages. It tells you that a number is being expressed as a fraction of 100. When you place this symbol after a number, it converts that number into a percentage.

For example, when we write 9%, it is the same as saying '9 per 100' or '9 out of 100'. This symbol is key in distinguishing between a decimal and a percentage. In everyday usage, percentages are everywhere, from calculating sales tax to determining interest rates. It's crucial for students to remember to add the symbol after converting from a decimal, as 9 is not the same as 9%, just as 0.09 is not the same as 9%. The symbol serves as a universal indicator that the number is a part of a whole broken down into a hundred units.