Virginia SOL 5.NS.2.a
The Standard
Given a whole number up to 100, create a concrete or pictorial representation to demonstrate whether the number is prime or composite, and justify reasoning.
Virginia Standards of Learning for Mathematics · The student will demonstrate an understanding of prime and composite numbers, and determine the prime factorization of a whole number up to 100.
Teacher's field guide
What This Standard Means
What Students Need to Do
- Students use counters, tiles, or drawings to make rectangular arrays for a number. They use the arrays and factor pairs to decide whether the number is prime or composite and explain why.
What Mastery Looks Like
- Students build or draw rectangular arrays to find factor pairs. They correctly classify numbers with exactly two factors as prime and numbers with more than two factors as composite.
Common Misconceptions
- Students may think every odd number is prime or every even number is composite, forgetting that 2 is prime. They may label 1 as prime or stop checking factors after trying only 2 and 3.
How to Assess It
- Give students 29 and 36. Ask them to draw possible arrays, label each number prime or composite, and justify each answer using factors.
Lesson moves
Ways to Teach It
Give pairs 36 counters to build every possible rectangular array, then list the factor pair shown by each array.
Ask students to explain in writing why 21 is composite and why 23 is prime, using factors or arrays as evidence.
Play Factor Sort with number cards from 1 to 100, placing each card under prime, composite, or neither.
Plan equal rows of 47 chairs for an assembly, then compare the possible arrangements with 48 chairs.
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Printable 5.NS.2.a Worksheet
A ready-to-print activity worksheet aligned to 5.NS.2.a, with an answer key for the teacher on its own page. No account needed.
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Related Standards
- 2.NS.2.g
Compare two whole numbers, each 999 or less, represented concretely, pictorially, or symbolically, using words (greater than, less than, or equal to) and symbol...
- 5.NS.2
The student will demonstrate an understanding of prime and composite numbers, and determine the prime factorization of a whole number up to 100.
- 4.CE.2.e
Determine all factor pairs for a whole number 1 to 100, using concrete, pictorial, and numerical representations.
- 5.NS.2.b
Classify, compare, and contrast whole numbers up to 100 using the characteristics prime and composite.
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