Understanding HCF and LCM

Lara and Lorenzo introduce the concepts of highest common factors (HCF) and lowest common multiples (LCM). They explain that factors are numbers that divide another number exactly, while multiples are the results of multiplying a number by integers. The video provides examples of finding HCF and LCM, using numbers like 16, 24, 15, and 25. The process involves listing factors or multiples, identifying common ones, and selecting the highest or lowest. The video concludes with practice examples and encourages viewers to engage further.

What is a factor of a number?

• A number that is subtracted to get another number

• A number that is added to get another number

• A number that is multiplied to get another number

• A number that divides another number exactly without leaving a remainder

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Which of the following is a multiple of 3?

• 7

• 11

• 9

• 5

What is the highest common factor (HCF) of 16 and 24?

• 4

• 6

• 8

• 12

Which step is NOT involved in finding the HCF?

• List all factors of each number

• Identify the highest factor common to both lists

• Compare the factors

• Multiply the numbers together

What is the first step in finding the LCM of two numbers?

• Add the numbers together

• Subtract the smaller number from the larger

• List multiples of each number

• List all factors of each number

What is the LCM of 16 and 24?

• 32

• 72

• 48

• 64

Which of the following is NOT a step in finding the LCM?

• Divide the numbers by their HCF

• List multiples of each number

• Find common multiples

• Choose the smallest common multiple

What is the HCF of 15 and 25?

• 3

• 5

• 10

• 15

What is the LCM of 15 and 25?

• 50

• 60

• 75

• 100

What is the LCM of 24 and 36?

• 48

• 60

• 72

• 84