LCM_and_HCF

Views:
 
Category: Education
     
 

Presentation Description

No description available.

Comments

Presentation Transcript

LCM and HCF:

LCM and HCF

Aims of this presentation::

Aims of this presentation: Understand what is meant by LCM and HCF Give a number as a product of primes Find LCM and HCF of sets of numbers

Lowest Common Multiple:

Lowest Common Multiple Write down the first 10 multiples of 5 7 6 8 What is the LCM of 5 and 7 5 and 6 6 and 8

Highest Common Factor:

Highest Common Factor Write down the factors of 30 56 40 21 What is the HCF of 30 and 40 30 and 56 21 and 40

Using a factor tree:

Using a factor tree 350

What are the factors of 350?:

What are the factors of 350? 350 = 2 x 5 2 x 7 Which of these must be factors and why 25 20 14 15 70 50 125

Write as a product of primes:

Write as a product of primes 400 320 650 260 728 2 4 x 5 2 2 6 x 5 2 x 5 2 x 13 2 2 x 5 x 13 2 3 x 7 x 13

Finding the HCF:

Finding the HCF Since 400 = 2 4 x 5 2 = 2 x 2 x 2 x 2 x 5 x 5 2 x 2 x 5 = 20 is a factor Since 260 = 2 2 x 5 x 13 = 2 x 2 x 5 x 13 2 x 2 x 5 = 20 is a factor Therefore 20 is a COMMON factor Since I chose ALL the values they had in common, 20 is the Highest Common Factor

What is the HCF of:

What is the HCF of 400 and 650 320 and 728 260, 650, and 728 260, 320, and 400 2 x 5 x 5 = 50 2 x 2 x 2 = 8 2 x 13 = 26 2 x 2 x 5 = 20

Co - Prime:

Co - Prime Some sets of numbers do not have prime factors in common 35 = 5 x 7 52 = 2 x 2 x 13 They still have a HCF The HCF = 1 These sets are Co-Prime

Which of these sets are co-prime:

Which of these sets are co-prime 20 and 65 35 and 48 50 and 28 33 and 55 63 and 40 42, 30, and 35 No (5) Yes No (2) No (11) Yes Yes

LCM:

LCM Explain why the LCM of 6 and 8 is NOT 48 400 x 650 = 260000 Is 260000 a Common Multiple of 400 and 650? Why? Is it the LCM of 400 and 650? Why? What is?

Ignoring the common factors:

Ignoring the common factors 650 = 2 x 5 x 5 x 13 728 = 2 x 2 x 2 x 7 x 13 To find the LOWEST common Multiple we can ignore the factors repeated in the second number LCM(650, 728) = 650 x 2 x 2 x 7 = 18200 LCM(650, 728) = 650 x 728 ÷ 26 = 18200

What is the LCM of:

What is the LCM of 320 and 650 260 and 728 400 and 320 20800 3640 1600