Finding the Lowest Common Multiple: Methods Explained

This video tutorial explains how to find the least common multiple (LCM) of a set of numbers. It covers the basic method of listing multiples and selecting the smallest common one, using examples with numbers like 6, 10, 5, and 8. The video also introduces a more efficient method using prime factors, demonstrated with examples involving numbers like 28, 42, 132, and 420. The tutorial emphasizes the importance of understanding the concept and practicing to become proficient.

What is the Least Common Multiple (LCM) of a set of numbers?

• The largest number that is a multiple of all the numbers in the set.

• The smallest number that is a multiple of all the numbers in the set.

• The sum of all the numbers in the set.

• The difference between the largest and smallest numbers in the set.

Which of the following is a correct method to find the LCM of two numbers?

• Adding the two numbers together.

• Listing the multiples of each number and finding the smallest common multiple.

• Subtracting the smaller number from the larger number.

• Dividing the larger number by the smaller number.

What is the LCM of 6 and 10?

• 60

• 20

• 30

• 40

Why is multiplying the numbers not always the best method to find the LCM?

• It sometimes gives a common multiple but not the least common multiple.

• It always gives the smallest common multiple.

• It is the fastest method.

• It is the most accurate method.

What is the LCM of 5 and 8?

• 40

• 30

• 20

• 50

What is a more efficient method to find the LCM for larger numbers?

• Adding the numbers.

• Listing all multiples.

• Using prime factorization.

• Subtracting the numbers.

When using prime factorization to find the LCM, what should you do if a prime factor appears in both lists?

• Ignore it.

• Count it only once.

• Subtract it from the total.

• Count it twice.

What is the LCM of 28 and 42 using prime factorization?

• 112

• 126

• 84

• 56

What is the LCM of 132 and 420 using prime factorization?

• 5880

• 4620

• 5460

• 5040

What is the final step in finding the LCM using prime factorization?

• Adding all the prime factors.

• Dividing the prime factors.

• Multiplying all the prime factors together.

• Subtracting the prime factors.