Factors And Primes
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Factors And Primes

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    Factors And Primes Factors And Primes Presentation Transcript

    • Multiples,Factors and Primes
    • Objectives
      • In this lesson you will get to work on
      • finding lowest common multiples
      • finding Factors of numbers
      • finding highest Common Factors
      • finding Prime numbers
    • Lowest Common Multiple
      • The lowest common multiple(LCM) of 3 and 4 is the lowest number which is in both the 3 and 4 times table.
      • First list out the 3 times tables:
      • 3, 6, 9, 12 ,15, ….
      • Then list out the 4 times table:
      • 4, 8, 12, 16, 20, 24….
      • The first number which comes up in both is 12.
      • 12 is the most common multiple of 3 and 4.
    • Questions
      • Find the LCM of these number pairs
      • 9 and 6
      • 8 and 12
      • 9 and 15
      • 24 and 18
      • The LCM can help us compare fractions.
      • Example which is bigger 1 / 6 or 3 / 8 ?
      • They are difficult to compare because they have different denominators(the bottom numbers)
      • 1 / 6 3 / 8
      • Find equivalent fractions which have a common denominator. (same bottom number)
    • To find the common denominator find the LCM of 6 and 8 Multiples of 8 are 8, 16, 24, 32.. Multiples of 6 are 6, 12,18, 24.. The LCM of 6 and 8 is 24 Now convert each fraction into 24ths 1 / 6 x 4 = 4 / 24 3 / 8 x 3 = 9 / 24 By finding a common denominator we can can now compare the fractions and see that 3/8 is bigger
      • What is a factor?
      • A number which divides exactly into another number is called a factor of that number.
      • Here is a way to find the factors of 20
      • Can 20 be divided by 1 exactly
      • 20 ÷ 1 = 20 20 ÷ 5 = 4
      • 20 ÷ 20 = 1 20 ÷ 4 = 5
      • 20 ÷ 2 = 10
      • 20 ÷ 10 = 2 We already have 5 as a factor. This
      • 20 ÷ 3 = No means we have listed all the factors of.
      • 20 ÷ 4 = 5 20. 1, 2, 4, 5, 10, 20
      • Defination
        • A number which divides exactly unto another number with no remainders is called a factor of that number.
        • List the factors of
        • 16
        • 1, 2, 4, 8, 16
        • 36
        • 1, 2, 3, 4, 6, 9, 12, 18, 36.
        • 100
        • 1, 2, 4, 5, 10, 20, 25, 50, 100
    • Highest Common Factors
      • What is the biggest number that 18 and 30 can be divided into without leaving a remainder
      • List the factors of 18
      • 1, 2, 3, 6, 9, 18
      • List the factors of 30. 1, 2, 3, 5, 6, 10, 15, 30
      • The biggest number in both lists is 6.
      • We say that the highest common factor of 18 and 30 is 6.
    • Questions
      • Find the highest common factors of
      • 6 and 15
      • 15 and 50
      • 12 and 66
      • 39 and 52
      • 21 and 36 and 60
    • Prime numbers
      • A prime number is a number that can only be divided by itself and the number 1.
      • Write down the prime numbers up to 20
      • 2, 3, 5, 7, 11, 13, 17, 19
    • Prime Factors
      • Can you list the prime factors of the following numbers. In other words list the factors and circle the ones which are prime numbers
      • 48
      • 1, 2, 3, 4, 6, 8, 12, 16, 24, 28
      • 25
      • 1, 5, 25
      • 17
      • 1, 17