LCM of 11 and 15
2026-02-28 19:05 Diff
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Last updated on August 5, 2025

The meaning of least common factor (LCM) is to find the smallest number that divides any two integers evenly. LCM is used mainly in fractions to find a common number for both the integers. We use LCM for solving problems, lining up cycles or even synchronizing of events, also to schedule tasks in everyday life.

What is the LCM of 11 and 15?

We use LCM of 11 and 15 to find  the smallest number that divides both the numbers equally.  The smallest positive number is the number that divides both numbers equally, is 165 without leaving any remainder. LCM is used mainly in fractions to find a common number for both the integers.
 

How to find the LCM of 11 and 15?

LCM of 11 and 15 using Division method:

In division method, we divide both the numbers, we begin with dividing side by side the smallest number. We continue dividing until we get a common number that divides both the numbers equally. It makes it easier for the children to focus on prime factors and identify them.

  • 3 divides 15 and not 11.
  • 5 divides 15 and not 11

Now multiply the divisors : 11×3×5=165, which is the LCM.
 

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LCM of 11 and 15 using Listing multiples:

Step 1: Start by listing multiples of both the numbers separately:


Multiples of 11 are 11,22,33,44,55,66,77,88,99,110,121,132,143,154,165…..'


Multiples of 15 are 15,30,45,60,75,90,105,120,135,150,165…..

Step 2: The least common factor from the list is 165. Therefore, the LCM of 11 and 15 is 165.

LCM of 11 and 15 using Prime factorization:

Step 1:We part both the numbers unto factors:


Factor of 11: 11


Factors of 15: 3×5

Step 2:Take the powers of both the numbers and multiply together:


LCM=11x3x5=165.

Common Mistakes and How to Avoid Them in LCM of 11 and 15

 While solving problems based on the LCM of 11 and 15, children fail to understand few concepts, to give an idea of the mistakes, given below are a few mistakes and solutions of how to avoid them:
 

Problem 1

Add the fractions 2x/11 and 3x/15=1

Okay, lets begin

To add the fractions, we need to  find the common denominator, and we need to find the LCM of the numbers (11 and 15)

LCM of 11 and 15


Prime factors of 11: 11


Prime factors of 15: 3×5


LCM = 11×3×5=165


2x/11, multiply both numerator and denominator with 15 to get 165 as the denominator.


 3x/15, multiply both numerator and denominator with 11 to get 165 as the denominator.


We get, 30x+33x/165=1


63x/165=1


63x=165


x=165/63=55/21


x=55/21.
 

Explanation

Answer :x=55/21.
 

Well explained 👍

Problem 2

Find the LCM of 11 and 15 to rewrite the mixed fractions 2 511 and 1215 with the same denominator.

Okay, lets begin

Convert the mixed fractions to improper fractions:


Explanation

So the fractions are 405/165 and 187/165.
 

Well explained 👍

Problem 3

If x/11+5/15=1, find the value of x.

Okay, lets begin

To add the fractions, we need to  find the common denominator, we need to find the LCM of the numbers 11 and 15.

LCM of 11 and 15


Prime factors of 11: 11


Prime factors of 15: 3×5


LCM = 3×5×11=165


 x/11  multiply both numerator and denominator with 15 to get 165 as the denominator.


5/15  Multiply both numerator and denominator with 11 to get 165 as the denominator.


We get,  15x + 55/165 = 1.


15x + 55=165


15x=165-55


x=110/15


x=22/3.
 

Explanation

Answer: x=22/3.

Well explained 👍

Problem 4

Use the division method to find the LCM of 11 and 15.

Okay, lets begin

      Divide the numbers by their prime factors:


                Step           11  15


                      3           11    5


                      5           11    1


                      11         1       1


 LCM = 3x 5 x11=165
 

Explanation

 LCM of 11 and 15  = 3x 5 x11=165
 

Well explained 👍

Problem 5

If LCM(11,15)=165 and a × b=330, what is GCF (a, b)?

Okay, lets begin

GCF (a, b)

= a x b / LCM (a,b)

= 330/165

=2.
 

Explanation

as we know LCM(11,15)=165.

Well explained 👍

FAQ’s on LCM of 11 and 15

1.What is the LCM of 15,11 and 12?

The LCM of 12,15 and 11 is 660.
 

2.There are how many factors in 3600?

 There are 45 factors of 3600, but the prime factors are 2,3,5.
 

3.Write the LCM of 11,15, and 21?

Prime factorization of 11= 11


Prime factorization of 15 = 5×3


Prime Factorization of 21 =7 × 3


LCM (12,15,21) = 32×7×5×11 = 1155.
 

4.Write six hundred and forty thousand in numbers?

‘Six hundred forty thousand’ is written as 640,000 in numbers.
 

5. What is the LCM of 17 and 19?

Important glossaries on the LCM of 15 and 11

  • Prime Factor: A natural number or whole number which has factors that are 1 and itself. For Example, 3 is a prime number.
  • Prime Factorization: The process of breaking down a number into its prime factors is called Prime Factorization. For example, the factorization of 14 is 2×7.
  • Co-prime numbers: numbers which has the only positive divisor of them both as 1. For example, 6 and 7.
     

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Hiralee Lalitkumar Makwana

About the Author

Hiralee Lalitkumar Makwana has almost two years of teaching experience. She is a number ninja as she loves numbers. Her interest in numbers can be seen in the way she cracks math puzzles and hidden patterns.

Fun Fact

: She loves to read number jokes and games.