Last updated on May 26th, 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.
We use LCM of 15 and 27 to find the smallest number that divides both the numbers equally. The smallest positive number is the number that divides both numbers equally, is 210 without leaving any remainder. LCM is used mainly in fractions to find a common number for both the integers.
The LCM of 15 and 27 can be found by the following methods like division method, listing multiples, prime factorization.
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.
Now multiply the divisors : 3×5×9=135 which is the LCM.
Start by listing multiples of both the numbers separately:
Multiples of 15 are 15,30,45,60,75,90,105,120,135…..
Multiples of 27 are 27,54,81,108,135…..
The least common factor from the list is 135. Therefore, the LCM of 15 and 27 is 135.
We part both the numbers unto factors:
Factor of 15: 3×5
Factors of 27: 33
Take the powers of both the numbers and multiply together:
LCM=33x5=135.
While solving problems based on the LCM of 15 and 27, 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:
Find the LCM of 15 and x, if the LCM is 60. What is the value of X?
X=4.
To add the fractions, we need to find the prime factorization of 15
Prime factors of 15: 3 × 5
The LCM of 15 and X is given as 60.
60= 22 x3x5
Since X shares factors with 60, the missing number should include 22 as 15 does not include any factor of 2.
Therefore,
X=22=4.
LCM of 15 and 4 is :
LCM(15,4)= 22 × 3 × 5 =60.
Thus, X=4.
Given two pairs of numbers (12,18) and (15,24) which pair has the greater LCM?
let us first find LCM of each pair:
LCM of 12 and 18:
Factorization of 12= 22 × 3
Factors of 18= 2x 32
Take the highest powers of both the numbers:
LCM(12,18)= 22 × 32 = 4 × 9=36
LCM of 15 and 24:
Factorization of 15= 3 × 5
Factorization of 24= 23 × 3
Take the highest powers of both the numbers:
LCM(15,24)= 23 × 3 × 5= 8 × 15=120.
LCM(15,24)= 120
LCM(12,18)= 36
so, (15,24 has greater LCM
Simplify the fraction 15/27 by finding the LCM of the numerator and the denominator’s greatest common divisor(GCD).
answer : 5/9
Prime Factorization of 15:
15=3 × 5
Prime Factorization of 27:
27=33
GCD of 15 and 27 is 3.
To simplify:
15/27 = 15÷3/27÷3 = 5/9.
If the LCM of two numbers a and b is 72, and their GCD is 4. Find the product of a and b.
product of a and b =288
LCM(a, b) x GCD (a, b)= a × b
LCM(a, b)=72 and GCD(a, b)=4
72 × 4= a × b
a × b =288.
If a=18 and LCM of a and b is 90, find b.
b=10.
by using the formula:
LCM(a, b)= a × b/GCD(a, b)
18=2x32 and the LCM is 90
Factors of 90 are 2 × 32 × 5
The missing factor is 5, so b =5 × 2 =10
b=10.
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.
: She loves to read number jokes and games.