Understanding Highest Common Factor (HCF)

The video tutorial explains how to find the highest common factor (HCF) for three or more numbers using factor trees. It begins with an introduction to HCF and prime numbers, followed by three examples demonstrating the technique. The first example shows the process for numbers 12, 24, and 36, while the second example highlights common mistakes when finding HCF for 22, 16, and 42. The final example uses numbers 10, 20, and 30 to reinforce the method. The video emphasizes the importance of identifying common prime numbers and multiplying them to find the HCF.

What is the largest number that divides exactly into two or more numbers called?

• Least Common Multiple

• Prime Factor

• Factor Tree

• Greatest Common Divisor

Which of the following is NOT a prime number?

• 2

• 4

• 5

• 7

In the factor tree method, what do you do after creating the factor trees for each number?

• Add all the numbers

• Look for common prime numbers

• Divide the numbers by 2

• Multiply all the numbers

What is the HCF of 12, 24, and 36?

• 6

• 8

• 12

• 18

When factoring 22, which two prime numbers are used?

• 5 and 11

• 2 and 13

• 3 and 7

• 2 and 11

What common mistake should be avoided when finding the HCF?

• Using a number not common to all

• Multiplying instead of adding

• Using non-prime numbers

• Forgetting to circle prime numbers

What is the HCF of 22, 16, and 42?

• 6

• 4

• 2

• 8

Which two numbers are the prime factors of 10?

• 2 and 3

• 2 and 5

• 5 and 7

• 3 and 5

What is the HCF of 10, 20, and 30?

• 5

• 10

• 15

• 20

What is the purpose of circling numbers in a factor tree?

• To highlight prime numbers

• To indicate numbers to be multiplied

• To mark numbers that are not factors

• To identify composite numbers