Prime and Composite Numbers Flashcards

Grade 5 · Math · Flashcards

Master the definitions and prime factorizations needed for Grade 5 number theory.

Flashcards

Prime number: A whole number greater than 1 with exactly 2 factors: 1 and itself. Examples: 2, 3, 5, 7, 11
Composite number: A whole number greater than 1 with more than 2 factors. Examples: 4, 6, 8, 9, 10
Is 1 prime or composite?: Neither — 1 has only one factor, so it does not qualify as prime or composite
Is 2 prime or composite?: Prime — it has exactly 2 factors (1 and 2) and is the only even prime number
Factor: A whole number that divides another evenly; example: factors of 12 are 1, 2, 3, 4, 6, 12
Prime factorization of 24: 2 x 2 x 2 x 3 (or 2³ x 3)
Prime factorization of 36: 2 x 2 x 3 x 3 (or 2² x 3²)
Prime factorization of 50: 2 x 5 x 5 (or 2 x 5²)
How to build a factor tree for 60: 60 = 6 x 10 = 2 x 3 x 2 x 5; prime factorization is 2 x 2 x 3 x 5
How to test if a number is prime: Check if any prime number up to its square root divides it evenly; if none do, it is prime
Is 51 prime or composite?: Composite — 51 = 3 x 17
Divisibility rule for 2: A number is divisible by 2 if it ends in 0, 2, 4, 6, or 8 (even numbers)
Divisibility rule for 3: A number is divisible by 3 if the sum of its digits is divisible by 3; example: 126 → 1+2+6=9, divisible by 3