Fifth Grade · Math · week 13

Subtract unlike fractions

Subtract fractions with unlike denominators using common denominators, and simplify the results.

Subtracting unlike fractions uses the exact same first move as adding: find a common denominator and rewrite both fractions. Then subtract the numerators instead of adding them.

Just like with addition, always check whether the result simplifies to an equivalent fraction in simplest form.

📋 For the teacher
Teach it (10–15 min):
  • Reuse the exact same routine as addition week, changing only the final operation -- it builds confidence that the hard part transfers.
  • Watch closely for "subtracting across" mistakes, where the denominators get subtracted too.
  • Encourage estimating first with benchmark fractions so an unreasonable answer stands out immediately.
  • Keep simplifying as the automatic last step, every single time.
Talk about it:
  • How is subtracting unlike fractions like adding them, and how is it different?
  • How can benchmark fractions help you estimate before subtracting?
  • What is the very last step you should always check?

Mastery looks like: They can subtract two unlike fractions by finding a common denominator, subtracting numerators, and simplifying.

Common stumbles: Subtracting the denominators along with the numerators; subtracting in the wrong order.

See it visually

Interactive, spoken-aloud tools that show this idea in motion.

FractionsSlice bars and circles into equal parts and compare them.try →SubtractionTake away and count back, step by step.try →
Homework for this lessonType it, write it with a stylus, or print it for pencil & paper.open →
Records attendance + 15 min of Math for this learner.
← Back to todayAll coursesYear planner