Year 6 Maths: Lowest Common Factors

What are Lowest Common Factors?

Hello, Year 6! Today, we’re going to learn about something called “Lowest Common Factors” (or LCF for short). This is a very useful concept in maths, especially when we work with numbers.

What is a Factor?

First, let’s remember what a factor is. A factor is a number that can divide another number without leaving a remainder. For example:

• The factors of 6 are 1, 2, 3, and 6 because:
  • $$6 \div 1 = 6$$
  • $$6 \div 2 = 3$$
  • $$6 \div 3 = 2$$
  • $$6 \div 6 = 1$$

What is a Common Factor?

Now, a common factor is a number that is a factor of two or more numbers. For example, if we look at the numbers 12 and 18:

• The factors of 12 are 1, 2, 3, 4, 6, and 12.
• The factors of 18 are 1, 2, 3, 6, 9, and 18.

The common factors of 12 and 18 are 1, 2, 3, and 6.

What is the Lowest Common Factor?

The Lowest Common Factor is just the smallest factor that two or more numbers share. In our example with 12 and 18, the common factors are 1, 2, 3, and 6. The lowest one is 1.

Key Rules

1. Always Include 1: The number 1 is always a common factor of any two numbers.
2. Find the Factors: List out the factors of each number.
3. Identify Common Factors: Look for numbers that appear in both lists.
4. Select the Lowest: Choose the smallest number from your common factors.

Tips and Tricks

• When finding factors, try dividing the number by smaller numbers first.
• You can use a factor tree to help you find factors easily.
• Remember, for any two numbers, the Lowest Common Factor will always be at least 1!

Let’s Practice!

Here are some questions for you to try. Let’s see how well you understand Lowest Common Factors!

Easy Level Questions

1. What are the factors of 10?
2. What are the factors of 15?
3. Which number is a common factor of 8 and 12?
4. What is the Lowest Common Factor of 4 and 8?
5. Which number is a common factor of 9 and 27?
6. What is the Lowest Common Factor of 6 and 9?
7. List the common factors of 10 and 20.
8. What is the Lowest Common Factor of 5 and 15?
9. Are 2 and 4 common factors of 8?
10. What is the Lowest Common Factor of 3 and 6?

Medium Level Questions

11. List the factors of 24.
12. What are the common factors of 18 and 30?
13. What is the Lowest Common Factor of 12 and 16?
14. Find the common factors of 15 and 25.
15. What is the Lowest Common Factor of 8 and 10?
16. Which number is a common factor of 14 and 49?
17. List the common factors of 16 and 24.
18. What is the Lowest Common Factor of 21 and 28?
19. Are 3 and 6 common factors of 12?
20. What is the Lowest Common Factor of 9 and 12?

Hard Level Questions

21. What are the factors of 36?
22. List all common factors of 45 and 60.
23. Find the Lowest Common Factor of 14 and 21.
24. What are the common factors of 24 and 30?
25. What is the Lowest Common Factor of 16 and 40?
26. Which number is a common factor of 50 and 100?
27. List the common factors of 28 and 42.
28. What is the Lowest Common Factor of 32 and 48?
29. Find the common factors of 18 and 54.
30. What is the Lowest Common Factor of 27 and 36?

Answers

Easy Level Answers

1. 1, 2, 5, 10
2. 1, 3, 5, 15
3. 1, 2, 4
4. 4
5. 1, 3, 9
6. 3
7. 1, 2, 5, 10
8. 5
9. Yes
10. 3

Medium Level Answers

11. 1, 2, 3, 4, 6, 8, 12, 24
12. 1, 2, 3, 6
13. 4
14. 5
15. 2
16. 7
17. 1, 2, 4, 8
18. 7
19. Yes
20. 3

Hard Level Answers

21. 1, 2, 3, 4, 6, 9, 12, 18, 36
22. 1, 3, 5, 15
23. 7
24. 1, 2, 3, 6
25. 8
26. 10, 25
27. 1, 2, 4
28. 4
29. 1, 2, 3, 6, 9
30. 9

I hope this helps you understand Lowest Common Factors better! Remember to practice, and you’ll become a factor expert in no time!