Write a Python Program to Find LCM

The Least Common Multiple (LCM) of two numbers is the smallest positive integer that is divisible by both numbers.

For example, the LCM of 4 and 6 is 12 because 12 is the smallest number that is divisible by both 4 and 6.

In this tutorial, we will write a Python program to find the LCM of two numbers using different methods.

Method 1: Using a Loop (Basic Approach)

# Taking user input
num1 = int(input("Enter first number: "))
num2 = int(input("Enter second number: "))

# Finding the maximum number between the two
max_num = max(num1, num2)

# Loop until we find the LCM
while True:
    if max_num % num1 == 0 and max_num % num2 == 0:
        lcm = max_num
        break
    max_num += 1

# Printing the result
print("LCM of", num1, "and", num2, "is:", lcm)

Output

Enter first number: 5
Enter second number: 15
LCM of 5 and 15 is: 15

Method 2: Using GCD (Efficient Approach)

The LCM can be found using the Greatest Common Divisor (GCD) with this formula:

import math

# Taking user input
num1 = int(input("Enter first number: "))
num2 = int(input("Enter second number: "))

# Using GCD formula to find LCM
lcm = abs(num1 * num2) // math.gcd(num1, num2)

# Printing the result
print("LCM of", num1, "and", num2, "is:", lcm)

Output

Enter first number: 12
Enter second number: 18
LCM of 12 and 18 is: 36

Method 3: Using a Function (Reusable Code)

import math

def find_lcm(a, b):
    return abs(a * b) // math.gcd(a, b)

# Taking user input
num1 = int(input("Enter first number: "))
num2 = int(input("Enter second number: "))

# Calling function
lcm = find_lcm(num1, num2)

# Printing the result
print("LCM of", num1, "and", num2, "is:", lcm)

Output

Enter first number: 8
Enter second number: 14
LCM of 8 and 14 is: 56