If you ask a student which fraction is larger between 4/7 and 5/9, they might struggle to guess. But with the cross-multiplication comparison test, you never have to guess or find a common denominator.

The 2-Second Test

  1. Write the two fractions side by side: 4/7 and 5/9.
  2. Multiply the bottom of the second fraction by the top of the first fraction: 9 × 4 = 36. Write 36 above 4/7.
  3. Multiply the bottom of the first fraction by the top of the second fraction: 7 × 5 = 35. Write 35 above 5/9.
  4. Compare the two numbers: 36 is greater than 35.
  5. Therefore: 4/7 > 5/9!

This quick trick saves valuable time on standardized tests and homework assignments.