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.
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.
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
- Fraction to decimal: Divide (color{blue}{text{ numerator } div text{ denominator }}). Add zeros after the decimal point as needed.
- Decimal to fraction: Write the digits over the place-value denominator (10, 100, 1000, …).
- Simplify the fraction using the GCF.
- 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.
- (color{blue}{frac{7}{8}}) (fraction to decimal)
- (color{blue}{frac{3}{5}}) (fraction to decimal)
- (color{blue}{frac{9}{20}}) (fraction to decimal)
- (color{blue}{0.8}) (decimal to fraction)
- (color{blue}{0.15}) (decimal to fraction)
- (color{blue}{0.375}) (decimal to fraction)
Answers
- (color{blue}{7 div 8 = 0.875})
- (color{blue}{3 div 5 = 0.6})
- (color{blue}{9 div 20 = 0.45})
- (color{blue}{0.8 = frac{8}{10} = frac{4}{5}})
- (color{blue}{0.15 = frac{15}{100} = frac{3}{20}})
- (color{blue}{0.375 = frac{375}{1000} = frac{3}{8}})
Frequently Asked Questions
What if the fraction gives a repeating decimal?
If the denominator (in lowest terms) has a prime factor other than 2 or 5, the decimal repeats. Write the repeating block with a bar over it. For example, (color{blue}{frac{1}{3} = 0.̅3}).
How do I convert a decimal greater than 1 (like 1.25) to a fraction?
Treat the whole-number part separately: (color{blue}{1.25 = 1 + 0.25 = 1 + frac{1}{4} = 1 frac{1}{4}}), which as an improper fraction is (color{blue}{frac{5}{4}}).
Why do I need to convert between fractions and decimals on the GED?
Many GED problems require comparing or combining values given in mixed forms. For example, comparing (color{blue}{frac{3}{5}}) and (color{blue}{0.65}) is easiest if you convert (color{blue}{frac{3}{5} = 0.60}) first, then compare.
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