Convert Between Fractions and Decimals

Convert Between Fractions and Decimals

How to convert between fractions and decimals, step by step: the rule in plain language, solved examples worked one line at a time, and practice questions so you can try it yourself before moving on.

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Converting between fractions and decimals is a fundamental skill for the GED Mathematical Reasoning test. You will need this ability to compare numbers, evaluate expressions, and solve real-world problems. Whether you are changing \(\color{blue}{\frac{3}{4}}\) to \(\color{blue}{0.75}\) or turning \(\color{blue}{0.6}\) into \(\color{blue}{\frac{3}{5}}\), the process is systematic and quick once you know the rules.

What Does It Mean to Convert Between Fractions and Decimals?

A fraction and a decimal are two different ways of writing the same value. For example, \(\color{blue}{\frac{1}{2} = 0.5}\) and \(\color{blue}{\frac{3}{4} = 0.75}\). Converting between them allows you to use whichever form is more convenient for a given problem.

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How to Convert a Fraction to a Decimal

Divide the numerator by the denominator

Every fraction means division. To convert, divide the top number by the bottom number.

  • \(\color{blue}{\frac{3}{4}}\): divide \(\color{blue}{3 \div 4 = 0.75}\)
  • \(\color{blue}{\frac{5}{8}}\): divide \(\color{blue}{5 \div 8 = 0.625}\)
  • \(\color{blue}{\frac{7}{20}}\): divide \(\color{blue}{7 \div 20 = 0.35}\)
  • \(\color{blue}{\frac{11}{25}}\): divide \(\color{blue}{11 \div 25 = 0.44}\)

If the division does not terminate, the decimal repeats (see the Repeating Decimals lesson).

How to Convert a Decimal to a Fraction

Use the place value

Write the decimal digits over the appropriate power of 10 (10 for tenths, 100 for hundredths, etc.), then simplify.

  • \(\color{blue}{0.6 = \frac{6}{10} = \frac{3}{5}}\)
  • \(\color{blue}{0.35 = \frac{35}{100} = \frac{7}{20}}\)
  • \(\color{blue}{0.125 = \frac{125}{1000} = \frac{1}{8}}\)
  • \(\color{blue}{0.4 = \frac{4}{10} = \frac{2}{5}}\)
  • \(\color{blue}{0.75 = \frac{75}{100} = \frac{3}{4}}\)

Step-by-Step Summary

  1. Fraction to decimal: Divide \(\color{blue}{\text{ numerator } \div \text{ denominator }}\). Add zeros after the decimal point as needed.
  2. Decimal to fraction: Write the digits over the place-value denominator (10, 100, 1000, …).
  3. Simplify the fraction using the GCF.
  4. Check by converting back: the fraction and decimal should produce the same value.

Watch: Convert Any Fraction to a Decimal (Video Lesson)

Math Antics shows an easy, reliable method for converting any fraction to a decimal using long division:


Convert Between Fractions and Decimals – Worked Examples

Example 1: Convert \(\color{blue}{\frac{3}{8}}\) to a decimal.

Divide: \(\color{blue}{3 \div 8 = 0.375}\). Answer: \(\color{blue}{0.375}\).

Example 2: Convert \(\color{blue}{0.625}\) to a fraction in lowest terms.

Place value: thousandths. \(\color{blue}{0.625 = \frac{625}{1000}}\). \(\color{blue}{\text{ GCF }(625, 1000) = 125}\). Divide: \(\color{blue}{\frac{625}{125} = 5}\), \(\color{blue}{\frac{1000}{125} = 8}\). Answer: \(\color{blue}{\frac{5}{8}}\).

Example 3: Convert \(\color{blue}{\frac{11}{25}}\) to a decimal.

Divide: \(\color{blue}{11 \div 25 = 0.44}\). Answer: \(\color{blue}{0.44}\).

Example 4: Convert \(\color{blue}{0.4}\) to a fraction in lowest terms.

\(\color{blue}{0.4 = \frac{4}{10}}\). \(\color{blue}{\text{ GCF }(4, 10) = 2}\). Simplify: \(\color{blue}{\frac{4}{10} = \frac{2}{5}}\).

More Practice: Converting Fractions to Decimals (Video)

Khan Academy reinforces fraction-to-decimal conversion with additional examples:


Exercises for Converting Fractions and Decimals

Convert each fraction to a decimal and each decimal to a fraction in lowest terms.

  1. \(\color{blue}{\frac{7}{8}}\) (fraction to decimal)
  2. \(\color{blue}{\frac{3}{5}}\) (fraction to decimal)
  3. \(\color{blue}{\frac{9}{20}}\) (fraction to decimal)
  4. \(\color{blue}{0.8}\) (decimal to fraction)
  5. \(\color{blue}{0.15}\) (decimal to fraction)
  6. \(\color{blue}{0.375}\) (decimal to fraction)

Answers

  1. \(\color{blue}{7 \div 8 = 0.875}\)
  2. \(\color{blue}{3 \div 5 = 0.6}\)
  3. \(\color{blue}{9 \div 20 = 0.45}\)
  4. \(\color{blue}{0.8 = \frac{8}{10} = \frac{4}{5}}\)
  5. \(\color{blue}{0.15 = \frac{15}{100} = \frac{3}{20}}\)
  6. \(\color{blue}{0.375 = \frac{375}{1000} = \frac{3}{8}}\)

Frequently Asked Questions

How do you convert between fractions and decimals?

To change a fraction to a decimal, divide the numerator by the denominator: 5/8 = 5 ÷ 8 = 0.625. To change a decimal to a fraction, read its place value, write it over 10, 100 or 1,000, and simplify: 0.625 = 625/1000 = 5/8. Practicing both directions with the same number is a good way to check your work.

What is the relationship between fractions and decimals?

A fraction and a decimal are two ways to write the same value, because a fraction bar simply means division. Decimals are fractions with denominators of 10, 100, 1,000 and so on, so 0.7 means 7/10 and 0.07 means 7/100. Knowing this link lets you pick the easier form on a GED question, for example decimals when using the calculator.

How do you convert between decimals and fractions or mixed numbers?

Write the whole-number part as the whole number and turn only the decimal part into a fraction. For 3.25, the 3 stays and 0.25 = 25/100 = 1/4, so 3.25 = 3 1/4. Going the other way, divide the fraction part and add it to the whole: 2 3/8 = 2 + 0.375 = 2.375.

How do you convert between repeating decimals and fractions?

A fraction gives a repeating decimal when its simplified denominator has a prime factor other than 2 or 5, such as 2/11 = 0.1818…. To go back, set x equal to the decimal, multiply by 10 for each repeating digit, and subtract. For x = 0.1818…, 100x = 18.1818…, so 99x = 18 and x = 18/99 = 2/11.

How do you turn fractions and decimals into percentages?

For a decimal, multiply by 100 and add the % sign: 0.08 becomes 8%. For a fraction, first divide to get a decimal, then multiply by 100: 7/8 = 0.875, which is 87.5%. A quick shortcut for decimals is to move the decimal point two places to the right.

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