Testinar Grade 5 math

Finding Common Denominators

Students will find common denominators and create equivalent fractions for computation.

CH04-01 Adding and Subtracting Fractions
Name
Date
Score
____ / 8
Directions Solve each problem. Show your reasoning on the page or on separate paper. Check the answer key only after finishing.

  1. What is a common denominator for \(\frac{1}{3}\) and \(\frac{1}{4}\)?

    1. 7
    2. 12
    3. 8
    4. 6

  2. Which number is a common denominator for \(\frac{2}{5}\) and \(\frac{3}{4}\)?

    1. 20
    2. 9
    3. 15
    4. 10

  3. Complete the table showing multiples. Which number is the least common denominator for \(\frac{1}{6}\) and \(\frac{1}{8}\)?

    Finding Common Denominators visual for G5-C03-T02-Q003
    1. 18
    2. 32
    3. 12
    4. 24

  4. Rewrite \(\frac{1}{3}\) and \(\frac{1}{4}\) with a common denominator of 12.

    Finding Common Denominators visual for G5-C03-T02-Q004
    1. \(\frac{4}{12}\) and \(\frac{3}{12}\)
    2. \(\frac{3}{12}\) and \(\frac{4}{12}\)
    3. \(\frac{2}{12}\) and \(\frac{5}{12}\)
    4. \(\frac{6}{12}\) and \(\frac{3}{12}\)

  5. List the first four multiples of 7.

    1. 1, 7, 14, 21
    2. 7, 14, 21, 35
    3. 7, 15, 21, 28
    4. 7, 14, 21, 28

  6. Which is the least common denominator for \(\frac{5}{6}\) and \(\frac{1}{4}\)?

    1. 24
    2. 12
    3. 8
    4. 6

  7. Compare the fractions \(\frac{2}{5}\) and \(\frac{1}{3}\) by finding a common denominator. Which statement is true?

    1. \(\frac{2}{5} < \frac{1}{3}\)
    2. \(\frac{2}{5} > \frac{1}{3}\)
    3. \(\frac{2}{5} = \frac{1}{3}\)
    4. Cannot compare

  8. Rewrite \(\frac{2}{3}\) and \(\frac{3}{5}\) with a common denominator.

    Finding Common Denominators visual for G5-C03-T02-Q009
    1. \(\frac{10}{15}\) and \(\frac{9}{15}\)
    2. \(\frac{6}{15}\) and \(\frac{9}{15}\)
    3. \(\frac{5}{15}\) and \(\frac{10}{15}\)
    4. \(\frac{8}{15}\) and \(\frac{7}{15}\)
Teacher and parent reference

Answer key and explanations

  1. B. 12

    Multiples of 3: 3, 6, 9, 12, \ldots{} Multiples of 4: 4, 8, 12, \ldots{} The least common multiple is 12, which is a common denominator.

  2. A. 20

    Multiples of 5: 5, 10, 15, 20, \ldots{} Multiples of 4: 4, 8, 12, 16, 20, \ldots{} The least common denominator is 20.

  3. D. 24

    From the table, 24 appears in both rows. The least common denominator is 24.

  4. A. \(\frac{4}{12}\) and \(\frac{3}{12}\)

    \(\frac{1}{3} = \frac{1 \times 4}{3 \times 4} = \frac{4}{12}\) and \(\frac{1}{4} = \frac{1 \times 3}{4 \times 3} = \frac{3}{12}\).

  5. D. 7, 14, 21, 28

    Multiples of 7 are found by multiplying 7 by 1, 2, 3, 4: \(7 \times 1 = 7\), \(7 \times 2 = 14\), \(7 \times 3 = 21\), \(7 \times 4 = 28\).

  6. B. 12

    Multiples of 6: 6, 12, 18, \ldots{} Multiples of 4: 4, 8, 12, \ldots{} The LCD is 12.

  7. B. \(\frac{2}{5} > \frac{1}{3}\)

    Common denominator is 15. \(\frac{2}{5} = \frac{6}{15}\) and \(\frac{1}{3} = \frac{5}{15}\). Since \(6 > 5\), \(\frac{2}{5} > \frac{1}{3}\).

  8. A. \(\frac{10}{15}\) and \(\frac{9}{15}\)

    \(\frac{2}{3} = \frac{2 \times 5}{3 \times 5} = \frac{10}{15}\) and \(\frac{3}{5} = \frac{3 \times 3}{5 \times 3} = \frac{9}{15}\).

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