Work Step by Step
Use the factor tree to find the prime factorization for each number: 4 and 4 are factors of 16. Neither are prime, but 2 and 2 are factors of 4 and are prime. So, 2x2x2x2 is the prime factorization for 16. 5 and 4 are factors of 20. 5 is prime but 4 is not. 2 and 2 are factors of 4 and are both prime. So, the prime factorization of 20 is 2x2x5. Use each prime number the greatest number of times it appears in either numbers' prime factorization. 2 appears the most (4 times) in 16 and 5 appears the most (1 time) in 20. Therefore, the LCM is 2x2x2x2x5 which equals 80.