Finding LCM and GCD Concepts

The video tutorial covers the concepts of Greatest Common Divisor (GCD) and Lowest Common Multiple (LCM). It begins with an introduction to GCD, explaining how to find it using prime factorization. The tutorial then transitions to LCM, describing its definition and methods to calculate it, including listing multiples and using prime factor trees. The video provides examples and encourages student participation to reinforce understanding.

What is the greatest common divisor (GCD) of 18 and 20?

• 4

• 2

• 5

• 3

Which of the following is the correct prime factorization of 18?

• 2 x 2 x 3

• 3 x 3

• 2 x 3^2

• 2 x 3

What is the lowest common multiple (LCM) of 3 and 5?

• 15

• 30

• 45

• 60

How does the LCM differ from the GCD?

• LCM is the largest number that divides both numbers.

• LCM is the smallest number that both numbers divide into.

• LCM is always smaller than GCD.

• LCM is the sum of the numbers.

Which of the following is a common multiple of 3 and 5?

• 9

• 10

• 15

• 20

What is the lowest common multiple of 18 and 30 using the listing method?

• 90

• 360

• 180

• 270

What is the first step in using prime factor trees to find the LCM?

• Add the numbers together.

• List all multiples of the numbers.

• Multiply the numbers directly.

• Find the prime factors of each number.

What is the LCM of 18 and 30 using prime factor trees?

• 360

• 270

• 180

• 90

Which of the following is a prime factor of 30?

• 4

• 8

• 2

• 6

What is the benefit of using prime factor trees to find the LCM?

• It is the only method to find LCM.

• It requires no calculations.

• It is more accurate than other methods.

• It is faster than listing all multiples.