Prime or Composite Sort

4th Grade MathFactors and Multiples4 pages

About this worksheet

A prime and composite sort for 4th grade on Common Core 4.OA.4. The callout settles definitions up front, including that 1 is neither. Twelve numbers in the bank (7, 12, 19, 21, 29, 33, 37, 45, 49, 51, 53 and 60) split five-and-seven into prime and composite columns, and every placement must be backed by its full list of factor pairs. The traps are deliberate: 49, 51 and 33 all look prime and are not. The closing challenge dismantles Maya's argument that 51 is prime because it ends in 1. Answers included.

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$Prime or Composite Sort: Factors and Multiples - page 1$

$Prime or Composite Sort: Factors and Multiples - page 2$

$Prime or Composite Sort: Factors and Multiples - page 3$

$Prime or Composite Sort: Factors and Multiples - page 4$

Curriculum objectives covered

4.OA.4

“Find all factor pairs for a whole number in the range 1-100. Recognize that a whole number is a multiple of each of its factors. Determine whether a given whole number in the range 1-100 is a multiple of a given one-digit number. Determine whether a given whole number in the range 1-100 is prime or composite.”

The twelve-number sort with factor-pair proof covers the prime-composite clause; the 51 challenge attacks the most common false rule for it.

What's inside this worksheet

Number Bank

Twelve numbers from 7 to 60 to cut out or copy into the chart, with 49 (7 × 7) and 51 (3 × 17) planted among the true primes.

Sorting Chart

Five numbered prime slots and seven composite slots, each with a factor-pairs line, so the counts themselves confirm a correct sort.

Math Reasoning Challenge

Maya reasons that 51 ends in 1 and is odd, so it must be prime. Students confirm or refute her with factor pairs, next to a detective illustration examining the number through a magnifying glass.

How teachers use it

Divisibility-by-3 moment

When someone slots 51 as prime, teach the digit-sum test on the spot: 5 + 1 = 6, so 3 divides it. The bank plants 33 and 45 for the same lesson.

Slot-count feedback

Tell students the chart has exactly five prime slots. A sixth "prime" means going back with a pencil, which is self-checking without you.

Homework variant

Assign the same sort with the numbers 50 to 61 written in planners. The sheet's structure transfers as is.

More 4th Grade Math worksheets

Multi-Digit Operations Fractions and Decimals Measurement and Data Geometry

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