Grade 4

Grade 4Factors and Multiples


Finding Common Multiples


It is very important to understand multiples and factors in math because they help us solve many mathematical problems. Today, we will focus on finding common multiples. This may seem complicated, but it is quite simple, especially with practice and understanding.

The factor of a number is the product you get when you multiply that number by an integer. Every number has an infinite number of factors. Let's look at this in more depth by finding the common multiples of numbers.

Understanding multiples

Let's start by understanding the multiples of a number. For example, consider the number 3:

Multiples of 3: 3, 6, 9, 12, 15, 18, 21, 24, 27, 30, ...

Here, each number (3, 6, 9, ...) is a multiple of 3 because it is obtained by multiplying 3 by some integer:

3 x 1 = 3
3 x 2 = 6
3 x 3 = 9
,
3 x 10 = 30

So basically, if you know a number and a list of integers, you can find its multiples by multiplying the number by each integer.

Finding common multiples

Now, let's consider two numbers. The task is to find the common multiples between them. Common multiples are numbers that are multiples of two or more numbers simultaneously.

For example, consider the numbers 3 and 4. To find the common multiple, let's list the first few multiples of each:

Multiples of 3:

3, 6, 9, 12, 15, 18, 21, 24, 27, 30, ...

Multiples of 4:

4, 8, 12, 16, 20, 24, 28, 32, ...

Now, identify the smallest multiples shared in both lists. The most straightforward way is to list these multiples and compare them. The smallest number that appears in both lists is:

12, 24, ...

The first common multiple of 3 and 4 is 12. The next common multiple is 24, and so on. These common multiples are the same in both sets.

Visualizing common multiples

To understand how common multiples work, let's look at a simple diagrammatic representation:

3, 6, 9, 12, ... 4, 8, 12, ... 12, 24, ...

In this diagram, the circles represent distinct multiples of 3 and 4. The overlapping area below represents common multiples, such as 12.

Working with large numbers

What if we need to find the common multiples of large numbers, such as 6 and 8?

Multiples of 6:

6, 12, 18, 24, 30, 36, ...

Multiples of 8:

8, 16, 24, 32, 40, ...

The step-by-step process remains the same. Compare the lists of multiples and see their overlap:

24, 48, ...

Here, 24 is the smallest common multiple of 6 and 8. The next term will be 48.

Least common multiple (LCM)

In mathematics, finding the smallest number in both lists is called finding the least common multiple (LCM).

To use the term correctly, the LCM of the numbers 6 and 8 is 24. The LCM is a useful concept, especially in solving problems that require the coordinate circle, such as adding fractions that have different denominators.

Why it's important: real-world applications

Understanding common multiples is not just an academic exercise; it has practical uses in real life too. Below are some examples where knowing about common multiples is useful:

  • Scheduling: If two events repeat after a certain number of days, then the LCM of those days helps to find out when the two events will occur again.
  • Music: Patterns in rhythm and beats are often repeated, and common multiples can synchronize these cycles.
  • Construction: When different parts need to fit together perfectly in cycles, common multiples help plan these iterations accurately.

Practice problems

Let's apply what we've learned so far to some problems:

  1. What are the common multiples of 5 and 10 up to 50?
    Solution:
    10, 20, 30, 40, 50
  2. Find the LCM of 7 and 14.
    Solution:
    14
  3. What are the first three common multiples of 4 and 6?
    Solution:
    12, 24, 36

Such exercises enhance understanding and help in mastering the concept of finding common multiples.

Conclusion

In short, finding common multiples is an essential part of understanding numbers and their relationships. It's easier when you break the problem down into steps: list the multiples, identify the common numbers, and sometimes find the smallest number among them. This process is not only useful for classroom math, but is also important in everyday activities that require an understanding of cycles and repetitions.

Now that you have the knowledge, it's time to practice and put these ideas into action. With repeated practice, finding common multiples becomes second nature and adds to your mathematical toolbelt, leaving you ready to tackle more complex problems as you go along.


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