6th grade · Math · Unit 9 of 19
Facts & Factors
Facts, primes, GCF and LCM
What your child practices
Quick recall of multiplication and division facts, plus factors, multiples and prime numbers, the greatest common factor (GCF) and least common multiple (LCM), and word problems that use them.
Texas Essential Knowledge and Skills (TEKS) teks student expectation: 6.7(A) · factors, multiples and prime factorization
How we explain it
Children can open this short lesson before they practice.
- A factor divides a number evenly. 3 and 4 are factors of 12.
- The greatest common factor (GCF) is the biggest factor two numbers share.
- The least common multiple (LCM) is the smallest multiple they share.
Example: Find the GCF of 12 and 18. Factors of 12: 1, 2, 3, 4, 6, 12. Factors of 18: 1, 2, 3, 6, 9, 18. The biggest shared one is 6. Answer: 6
Facts & Factors in Texas
In the Texas Essential Knowledge and Skills (TEKS), this is unit 9 of 19 in 6th grade Math, after Powers and Common Factors and before Algebra Moves.
Gradelings describes a child's practice on this unit as Beginning, Approaching, Meeting or Exceeding (Four practice steps). That reflects practice, not a report-card mark: the teacher decides the mark.
Source: Texas Education Agency (TEA)
Sample questions
A taste of this unit. In the app, questions change every time and get easier or harder to match your child.
Question 1
What is the least common multiple (LCM) of 9 and 4?
answer box
36
Hint: List multiples of the bigger number: 9, 18, 27… Stop at the first one that 4 also divides into evenly.
Question 2
What is 7 × 6?
7 × 6 = ?
answer box
42
Hint: Split 7 into 5 + 2: 6 × 5 = 30 and 6 × 2 = 12. Add them.
Question 3
What number goes in the box?
7 × = 35
- 3
- 7
- 5
- 6
5
Hint: Divide to find a missing factor: 35 ÷ 7.
Question 4
What is the greatest common factor (GCF) of 28 and 8?
answer box
4
Hint: List the factors of each number. The GCF is the biggest number that appears in both lists.
Question 5
Which of these numbers is prime?
- 27
- 29
- 51
- 21
29
Hint: A prime number has exactly two factors: 1 and itself. Test each number by dividing by 2, 3, 5 and 7. For example, 27 = 3 × 9, so 27 is not prime.
Question 6
Lena has 28 red beads and 20 blue beads. Lena wants to pack them into identical bags with nothing left over. What is the greatest number of bags Lena can make?
- 5
- 20
- 7
- 4
4
Hint: Identical bags with nothing left over means the number of bags must divide both 28 and 20. Find the greatest common factor.