Numbers Finder by Sum and LCM

Input the sum and LCM of two numbers to quickly determine the two numbers.

Calculate Numbers Based on Their Sum and LCM

Result

How to Calculate Numbers Based on Their Sum and LCM

Given two numbers \( x \) and \( y \), where: Sum: \( x + y = S \) Least Common Multiple (LCM): \( \text{LCM}(x, y) \)

Follow these steps to find the two numbers:

  1. List all factors of the LCM: Identify all factors of the given \( \text{LCM} \). These factors represent potential values for \( x \) and \( y \).
  2. Filter pairs that sum to \( S \): From the factor list, select pairs \( (x, y) \) where \( x + y = S \).
  3. Verify the LCM: For each selected pair \( (x, y) \), calculate their LCM and check if it matches the given \( \text{LCM} \). If it does, the pair is the solution.

Examples

Example 1: The sum of two numbers is 144, and their least common multiple is 420. Find the two numbers.

Solution:

1. List all factors:

Factors of 420: 1, 2, 3, 4, 5, 6, 7, 10, 12, 14, 15, 20, 21, 28, 30, 35, 42, 60, 70, 84, 105, 140, 210, 420.

2. Filter pairs (sum = 144):

Potential pairs: \( (4, 140) \), \( (60, 84) \).

3. Verify the LCM:

\( \text{LCM}(4, 140) = 140 \), Does not match.

\( \text{LCM}(60, 84) = 420 \), Matches.

Result: The two numbers are 60 and 84.

Example 2: The sum of two numbers is 272, and their least common multiple is 960. What are the numbers?

Solution:

1. List all factors:

Factors of 960: 1, 2, 3, 4, 5, 6, 8, 10, 12, 15, 16, 20, 24, 30, 32, 40, 48, 60, 64, 80, 96, 120, 160, 192, 240, 320, 480, 960.

2. Filter pairs (sum = 272):

Potential pairs: \( (32, 240) \)、\( (80, 192) \).

3. Verify the LCM:

\( \text{LCM}(32, 240) = 480 \), Does not match.

\( \text{LCM}(80, 192) = 960 \), Matches.

Result: The two numbers are 80 and 192.

Example 3: The sum of two numbers is 2000, and their least common multiple is 21879. What are the numbers?

Solution:

1. List all factors:

Factors of 21879: 1, 3, 9, 11, 13, 17, 33, 39, 51, 99, 117, 143, 153, 187, 221, 429, 561, 663, 1287, 1683, 1989, 2431, 7293, 21879.

2. Filter pairs (sum = 2000):

Potential pair: \( (11, 1989) \).

3. Verify the LCM:

\( \text{LCM}(11, 1989) = 21879 \), Matches.

Result: The two numbers are 11 and 1989.