Math Kangaroo USA
International Competition in Mathematics
for K-12 students

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Fraction 1

Fraction 1

Hints:

  1. Why can’t 5 be one of the numbers used?

  2. Why can’t 7 be one of the numbers used?

  3. Try looking for compatible denominators—what values allow the fractions to combine neatly?

Solution:

To narrow down the possibilities, notice a few key constraints:

  • Improper fractions can’t be used—so all fractions must be less than 1.

  • The fractions must be equal and expressed using single-digit numerators and denominators.

  • Denominator 5 cannot be used: any fraction with 5 as a denominator would require another 5 or a 0 to make an equivalent fraction using only single digits, which is not possible.


Strategy:

We’re looking for sets of equal fractions formed by two or more different single-digit fractions. Start by exploring pairs of denominators and checking whether the resulting fractions are equal.


Testing Fraction Pairs (Denominator combinations):

  • 4 & 8:

    • 1/4=2/8 ❌ (but 2 is not equal to 1)

    • 2/4=4/8

    • 3/4=6/8=9/12

  • 2 & 8:

    • 1/2=4/8 ❌ (numerators don’t match)

  • 6 & 8:

    • 3/6=4/8

  • 3 & 6:

    • 1/3=2/6

    • 2/3=4/6

  • 4 & 6:

    • 2/4=3/6=9/18


Valid Solutions:

We find two valid sets of equal single-digit fractions:

  1. 3/4=6/8=9/12
  1. 2/4=3/6=9/18

Conclusion:

There are exactly two sets of equal fractions that use only single-digit numerators and denominators:

  • 3/4=6/8=9/12

  • 2/4=3/6=9/18

These sets are found by checking pairs with compatible denominators and ensuring all values remain within single-digit limits.