CheerMath

Grade 5 Factors, Multiples & Primes Practice

Find What Numbers Share

See what numbers have in common! Work with bigger numbers, find common factors and common multiples, meet the GCF and the LCM, use the GCF to simplify fractions, and start reading factor trees.

Also known as Class 5 maths — the same topics, whether your school calls it grade, class or year.

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Sample questions

A few samples from this topic — try one, then show the answer.

  1. Find Common Factors

    The greatest common factor of 15 and 20 is □\square.
    Show answer
    Answer:
    5

  2. Find Common Factors

    The GCF of two numbers is 5. If one number is 10, what could the other be?
    • 2
    • 3
    • 7
    • 5
    Show answer
    Answer:
    5

  3. Find Common Multiples

    From the set {12,33,66,99,117,132,144}\{{ 12, 33, 66, 99, 117, 132, 144 }\}, which are common multiples of 3 and 11?
    • 12, 33, 117
    • 33, 66, 99, 132
    • 66, 144
    • 33, 66, 132, 144
    Show answer
    Answer:
    33, 66, 99, 132

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A worked example

The greatest common factor of 15 and 20 is □\square.
  1. Find the GCF of 15 and 20. To do this, first find all factors of each number by dividing.
  2. Find the factors of 15:\\15  ÷  \; \div \;1  =  \; = \;15→\to1 and 15 are factors\\15  ÷  \; \div \;2  =  \; = \;7 remainder 1→\to2 is not a factor\\15  ÷  \; \div \;3  =  \; = \;5→\to3 and 5 are factors\\We stop checking at 3. If we try 4: 15  ÷  \; \div \;4  =  \; = \;3 remainder 3. The quotient (3) is now smaller than the divisor (4), so any factor from here would already have appeared above. All factors have been found.
  3. Factors of 15 →\to1, 3, 5, 15
  4. Factors of 20 →\to1, 2, 4, 5, 10, 20
  5. Common factors →\to1, 5
  6. The greatest common factor is 5.

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