LCM Of 3, 5 and 15

The LCM or the least common multiple of 2 numbers is the smallest number that appears as a multiple of both numbers. In case of 3, 5 and 15, The LCM is 15. But how did we get to this answer? There are different ways to obtain a LCM of 2 or more numbers. Let us take a look at those methods.
 

Remember that we previously said there are plenty of ways to calculate the LCM of two numbers or more. Then some of those methods make it extremely easy for us to find the LCM of any two numbers. Those methods are: 

• Listing of Multiples

• Prime Factorization

• Division Method

Finally, now we will learn how each of these methods can help us to calculate LCM of given numbers.
 

This method will help us find the LCM of the numbers by listing the multiples of the given numbers. Let us take a step by step look at this method.

step 1: list all the multiples of the given numbers.

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

Multiples Of 5: 5, 10, 15, 20, 25, 30, 35, 40, 45 and 50.

Multiple Of 15: 15, 30, 45, 60, 75, 90, 105, 120, 135 and 150.

step 2: find the smallest common multiples in both the numbers. In this case, that number is 15 as highlighted above.

By this way we will be able to tell the LCM of given numbers.
 

Let us break down the process of prime factorization into steps and make it easy for children to understand.
The first step is to break down the given numbers into its primal form. The primal form of the number is:

3= 3

5= 5

15= 5×3

As 5 and 3 are common, it will be considered only once. We will get the equation as (5×3)

So after the multiplication, we will be getting the LCM as 15.

As you can see, using this method can be easier for larger numbers compared to the previous method. 
 

The method to calculate the LCM is really simple. We’ll break these given numbers apart till it comes down to one, by dividing it by the prime factors. The product of the divisors that will come is the LCM of the given numbers.

Let us understand it step by step:

The first thing is to find the number common in both the numbers. Here it is 3. In that case, we divide the numbers by 3. It will reduce the values of the numbers to 1, 5 and 5.

As 5 is a prime number, it can be divided by themselves. After this step, all the numbers in the last row will be 1.

This is the end of division. However, we will now find the product of the numbers on the left. The numbers on the left side are: 3 and 5. 

These numbers multiplied give 15. On this basis, therefore, the LCM of the 3, 5 And 15 becomes 15.
 

• Least Common Multiple (LCM): The smallest number that can be evenly divided by two or more given numbers.

• Prime Factorization: Breaking down a number into its prime factors, which are the prime numbers that multiply together to give the original number.

• Prime Numbers: Numbers greater than 1 that have no positive divisors other than 1 and themselves (e.g., 2, 3, 5, 7).

• Division Method: A technique for finding the LCM by dividing the given numbers by their prime factors until all are reduced to one.