Subtracting Fractions
Part of the Factors & Fractions section of Coddy's Pre-Algebra journey. Lesson 30 of 58.
Subtracting works exactly like adding: make the denominators match, then subtract the tops and keep the bottom. 4/5 - 1/3: 15 is a multiple of 5 and of 3. 4/5 is 12/15 and 1/3 is 5/15, so the line becomes 12/15 - 5/15, and 12 minus 5 is 7: 7/15.
The bottom stays 15 for the same reason as before. It names the size of the pieces, and taking some pieces away does not resize the ones that are left.
You can check a difference by adding back what you took away: 7/15 + 5/15 is 12/15, the fraction you started from. And as always, simplify at the end if the top and the bottom share a factor.
Challenge
Work out 5/6 - 1/4. Rename both fractions over a common denominator, then subtract.
Try it yourself
Simplify the expression
Test yourselfThis lesson includes a short quiz. Start the lesson to answer it and track your progress.
All lessons in Factors & Fractions
1Factors and Multiples
What a Factor IsFactor PairsDivisibility RulesMultiplesPrime or CompositeRecap: Factors and Multiples4What a Fraction Is
Parts of a WholeFractions on the LineA Fraction of a NumberImproper FractionsRecap: What a Fraction Is7Multiplying Fractions
Top Times TopCancel FirstWhole Times FractionA Fraction of a FractionRecap: Multiplying Fractions10Fractions in Stories
Part of a GroupWhat Is LeftSharing a FractionScaling a RecipeRecap: Fraction Stories2Prime Factorization
Factor TreesUsing ExponentsOne Tree per NumberBigger NumbersRecap: Prime Factorization5Equivalent Fractions
Same Amount, New NameSimplifying FractionsSimplify in StepsComparing FractionsRecap: Equivalent Fractions