Math
Adding Fractions by Adding the Denominators
Adding straight across the top and bottom instead of finding a common denominator first.
Quick check
Why students make it
Addition feels like it should work the way multiplication does, where you do go straight across. Fractions need a common denominator first, and that step is easy to skip.
The rule done right
Rewrite both fractions over a common denominator, then add only the numerators and keep the denominator the same.
Related resources
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Math: Adding and Subtracting Unlike Fractions Infographic -
Adding Fractions Infographic -
Equivalent Fractions Infographic -
Fractions: Half and Whole Infographic - Adding & Subtracting Fractions Cheat Sheet
- Fractions, Decimals & Percents Cheat Sheet
- Mixed Numbers & Improper Fractions Cheat Sheet
- Adding and Subtracting Fractions Worksheet
- Equivalent Fractions: Finding Equal Parts Worksheet
- Comparing Fractions with Unlike Denominators Worksheet
- Math: Equivalent Fractions Worksheet
- Fraction Operations Visualizer Tool
- Fractions on a Number Line Tool
- Fraction Wall & Equivalent Fractions Builder Tool
- Decimal, Fraction & Percent Converter Tool
- Mixed Numbers & Improper Fractions Builder Tool
- Fraction Operations & Equivalents Lab Lab
- Recipe Fractions & Mixing Lab Lab
- Place Value, Decimals & Scientific Notation Lab Lab