Virginia SOL 5.NS.2.c
The Standard
Determine the prime factorization for a whole number up to 100.
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 break a whole number into factors until every factor is prime. They record the result as a product of primes and check it by multiplying.
What Mastery Looks Like
- Given any number from 2 through 100, a student can use a factor tree or repeated division and reach the same prime factors. The student identifies when the work is complete and verifies the product.
Common Misconceptions
- Students may stop at composite factors, such as writing 36 = 4 × 9. They may treat 1 as prime, omit repeated prime factors, or think different factor trees produce different answers.
How to Assess It
- Exit ticket: Find the prime factorization of 84 using a factor tree, then multiply your prime factors to verify the result.
Lesson moves
Ways to Teach It
Give pairs 24 tiles to arrange into factor rectangles, then build a factor tree and circle every prime leaf.
Ask students to explain why 36 = 4 × 9 is a factorization but not a prime factorization.
Play Factor Tree Relay with number cards from 2 to 100, awarding a point only when every final factor is prime.
Use 60 snack bags as a packing context, then identify the prime factors behind all possible equal group sizes.
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Related Standards
- 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.
- 5.NS.2.a
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.
- 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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