Finding GCF and LCM Using Prime Factors

This video tutorial explains how to find the Least Common Multiple (LCM) and Greatest Common Factor (GCF) of the numbers 14 and 21 using a factor tree method. The instructor demonstrates the process of prime factorization for both numbers and then uses these factors to calculate the LCM by multiplying the highest power of each prime number. The GCF is found by identifying the common prime factors. The video concludes with a call to action to subscribe for more math and science tutorials.

What is the purpose of using a factor tree in finding LCM and GCF?

• To add the numbers

• To identify prime factors

• To simplify the numbers

• To subtract the numbers

Which prime numbers are factors of 14?

• 2 and 3

• 3 and 7

• 2 and 7

• 5 and 7

What is the prime factorization of 21?

• 2 and 7

• 3 and 7

• 2 and 3

• 5 and 7

How do you determine the LCM using the prime number chart?

• Subtract all prime numbers

• Divide all prime numbers

• Multiply all prime numbers, using each pair only once

• Add all prime numbers

What is the LCM of 14 and 21?

• 42

• 21

• 28

• 14

What should you do if you have a pair of numbers that are the same when finding the LCM?

• Use both numbers

• Use only one of the numbers

• Ignore the numbers

• Add the numbers

What is the rule for finding the GCF using the prime number chart?

• Use vertical pairs only

• Use all numbers

• Use diagonal pairs

• Use all horizontal pairs

What is the GCF of 14 and 21?

• 2

• 3

• 14

• 7

Which number cannot be used in finding the GCF of 14 and 21?

• 14

• 2

• 3

• 7

What is the main takeaway from the video?

• LCM and GCF can be found using division

• LCM and GCF can be found using addition

• LCM and GCF can be found using subtraction

• LCM and GCF can be found using a factor tree and prime number chart