Students start by correcting three classic mistakes: the GCF of 12 and 18 written as 3, the claim that every even number is composite, and the LCM of 4 and 8 listed as 32. Part B fills in the GCF of 20 and 30, the LCM of 3 and 7, and the missing factor of 32. Each question forces fourth graders to slow down and check whether a number actually divides both values evenly.
Part C asks for the difference between GCF and LCM with an example, plus every prime number between 10 and 20. The mix builds the careful reasoning needed before fractions arrive in Grade 5.
Style:
Factors and Multiples
Part A: Fix the Sentence
Each sentence has an error. Rewrite it correctly on the line.
1. Fix the sentence:
The GCF of 12 and 18 is 3.
Rewrite: The GCF of 12 and 18 is 6, because 6 is the largest number that divides both evenly.
2. Fix the sentence:
Every even number is composite.
Rewrite: Every even number greater than 2 is composite. The number 2 is even and prime.
3. Fix the sentence:
The LCM of 4 and 8 is 32.
Rewrite: The LCM of 4 and 8 is 8, because 8 is already a multiple of 4.
Part B: Fill in the Blank
Write the missing word or number on each line.
1. The GCF of 20 and 30 is 10.
2. The LCM of 3 and 7 is 21.
3. The factors of 32 are 1, 2, 4, 8, 16, and 32.
4. The number 42 is divisible by 2, 3, 6, 7, and 14.
Part C: Short Answer
Answer each question in one or two complete sentences.
1. What is the difference between GCF and LCM? Give an example.
The GCF is the greatest factor two numbers share, while the LCM is the smallest multiple they share. For 6 and 8, the GCF is 2 and the LCM is 24.
2. Name all the prime numbers between 10 and 20.
The prime numbers between 10 and 20 are 11, 13, 17, and 19.
Factors and Multiples
★ Part A: Fix the Sentence
Each sentence has an error. Rewrite it correctly on the line.
1) Fix the sentence:
The GCF of 12 and 18 is 3.
Rewrite: The GCF of 12 and 18 is 6, because 6 is the largest number that divides both evenly.
2) Fix the sentence:
Every even number is composite.
Rewrite: Every even number greater than 2 is composite. The number 2 is even and prime.
3) Fix the sentence:
The LCM of 4 and 8 is 32.
Rewrite: The LCM of 4 and 8 is 8, because 8 is already a multiple of 4.
★ Part B: Fill in the Blank
Write the missing word or number on each line.
1) The GCF of 20 and 30 is 10.
2) The LCM of 3 and 7 is 21.
3) The factors of 32 are 1, 2, 4, 8, 16, and 32.
4) The number 42 is divisible by 2, 3, 6, 7, and 14.
★ Part C: Short Answer
Answer each question in one or two complete sentences.
1) What is the difference between GCF and LCM? Give an example.
The GCF is the greatest factor two numbers share, while the LCM is the smallest multiple they share. For 6 and 8, the GCF is 2 and the LCM is 24.
2) Name all the prime numbers between 10 and 20.
The prime numbers between 10 and 20 are 11, 13, 17, and 19.
Ready to Practice?
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9 Questions
15-20 minutes
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