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Cogito

Grade 4 Math · Chapter 4 · Lesson 2

Practice Worksheet

Prime and Composite

Numbers that make only one rectangle.

10 problems · about 14 minutes · 4.OA.B.4

NameDate

Figure — use these to answer the problems

Try to make a rectangle other than one long row. Primes will not allow it.

1 × 7 = 7

Rows1
In each row7
Figure 1

Warm-Up Review

From earlier lessons. Loosen up before the new work.

2 problems

  1. From “Factor Pairs”

    How many factors does 36 have?

    Answer

  2. From “Multistep Word Problems”

    7 × 24 − 68 = ?

    Answer

Warm Up

Straightforward practice. Get the method working first.

4 problems

  1. Is 29 prime?

    • Yes.
    • No.

  2. Why is 1 not a prime number?

    • It has only one factor, not two.
    • Because it is too small.

  3. Is 17 prime?

    • Yes.
    • No.

  4. Is 27 prime?

    • No. 3 × 9 = 27.
    • Yes.

Build It Up

The same ideas with more to keep track of.

2 problems

  1. How many factors does a prime number have?

    Answer

  2. What is the only even prime number?

    Answer

Stretch Yourself

Mixed problems. Work out what kind of question it is before you start.

2 problems

  1. The Class

    13 children want equal rows of more than one. Is it possible?

    • No. 13 is prime.
    • Yes.

  2. The Other Class

    15 children in equal rows of more than one. How many in each row, if there are 3 rows?

    Answerchildren