LCM of two numbers without built-in functions

LCM of Two Numbers

LCM (Least Common Multiple) of two given numbers without using built-in math functions or user-defined functions.

# LCM of two numbers without use of built-in functions.

# Input two numbers

num1 = int(input("Enter first number: "))

num2 = int(input("Enter second number: "))

# Store the maximum of num1 and num2

if num1 > num2:

    max_num = num1

else:

    max_num = num2

# Find LCM using loop

while True:

    if (max_num % num1 == 0) and (max_num % num2 == 0):

        lcm = max_num

        break

    max_num += 1

# Display the result

print("LCM of", num1, "and", num2, "is", lcm)

Output of program

Enter first number: 5

Enter second number: 7

LCM of 5 and 7 is 35

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Python program to find LCM of Two Numbers

LCM of Two Numbers

Following python program will find the LCM of two given numbers.

import math

a = int(input("Enter first number: "))

b = int(input("Enter second number: "))

lcm = abs(a*b) // math.gcd(a, b)

print(f"LCM of {a} and {b} is {lcm}")

Output of program 

Enter first number: 5 Enter second number: 7 LCM of 5 and 7 is 35

Explanation

LCM (Least Common Multiple) is the smallest number that is divisible by both numbers.

In other words:

• It must be a multiple of 5
• It must be a multiple of 7
• And it should be the smallest such number.

List multiples of each number

• Multiples of 5: 5, 10, 15, 20, 25, 30, 35, 40, …
• Multiples of 7: 7, 14, 21, 28, 35, 42, …

Find the first common multiple

Looking at both lists:

• The first number that appears in both lists is 35.

So, LCM(5, 7) = 35.

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