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4th grade · Math · Unit 12 of 15

Prime & Composite

Count factors to sort numbers into prime and composite

What your child practices

A prime number has exactly two factors, 1 and itself (like 7). A composite number has more than two (like 12). 1 is neither. Children find factors with multiplication and division facts.

California Content Standards learning standard: 4.OA.4 · finding factor pairs and telling prime from composite numbers

How we explain it

Children can open this short lesson before they practice.

  1. A factor divides a number with none left over.
  2. A prime number has exactly 2 factors: 1 and itself.
  3. A composite number has more than 2 factors.

Example: Is 22 prime or composite? 22 ÷ 2 = 11, so 2 is a factor. It has more than 2 factors. Answer: Composite

Sample questions

A taste of this unit. In the app, questions change every time and get easier or harder to match your child.

  1. Question 1

    Which number is composite?

    • 3
    • 9
    • 17
    • 19

  2. Question 2

    Which number is a factor of 20?

    • 12
    • 4
    • 14
    • 6

  3. Question 3

    What number goes in the box?

    6 × = 36

    answer box

  4. Question 4

    Which statement is true?

    • Every number greater than 1 is prime
    • Every odd number is prime
    • Every even number is prime
    • Every even number greater than 2 is composite

  5. Question 5

    How many factors does 31 have?

    • 7
    • 1
    • 2

  6. Question 6

    Is 33 prime or composite?

    • neither prime nor composite
    • prime
    • composite

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