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Ch. 5 Math notes

Ch. 5 Math notes. Name: ____________________. 5.1 Factors, Multiples, Divisibility. Rules: a number is divisible by: 2 – if the last digit is even 3 – if the sum of the digits in divisible by 3 4 – if the number formed by the last two digits is divisible by 4

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Ch. 5 Math notes

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  1. Ch. 5 Math notes Name: ____________________

  2. 5.1 Factors, Multiples, Divisibility • Rules: a number is divisible by: • 2 – if the last digit is even • 3 – if the sum of the digits in divisible by 3 • 4 – if the number formed by the last two digits is divisible by 4 • 5 – if the last digit is 0 or 5 • 6 if the number is divisible by 2 AND 3 • 9 – if the sum of the digits is divisible by 9 • 10 – if the last digit is 0

  3. Divisibility -- Try these out: • Is 168 divisible by 2? • (why) • Is 168 divisible by 3? • (why) • Is 316 divisible by 4? • (why) • Is 195 divisible by 5? • (why) • Is 168 divisible by 6? • (why) • Is 549 divisible by 9? • (why) • Is 450 divisible by 10? • (why)

  4. Factors: • Are numbers that go into the number • A factor is smaller than the number you are finding the factor for, for instance if you are finding the factors for 45, they CANNOT be bigger than 45 • It is the rainbow • For instance the factors of 28: 1, 2, 4, 7, 14, 28 • Always start with 1 and the number and then work your way in • If a number is multiplied by itself you write it once

  5. Factors – try these: • 36 • 12 • 100

  6. Multiples • Multiples are answers when you take a number and multiply by it by something else • For instance if you find the multiplies of 4, it is just like writing the fact tables of 4 • 4, 8, 12, 16, 20 • Multiples are unlike factors in the fact that they are always BIGGER than the number.

  7. Multiples – Try these • 12 • 20 • 8

  8. 5.2 Prime Factorization • A prime number can only be divided EVENLY by 1 and itself – for instance 13, 17, 23 • A composite number can be divided by different numbers (it is every number that is NOT prime) • Prime factorization – is when you break the number down to only the prime numbers • If it is prime – it cannot be broken down any further than the number itself

  9. Try these: • 68 • 490 • 210

  10. 5.3 Greatest Common Factor (GCF) • Is the greatest number that is a factor of two or more numbers • The biggest number that can evenly go INTO a set of numbers • 12 and 18 • 12: 1, 2, 3, 4, 6, 12 • 18: 1, 2, 3, 6, 9, 18 • The numbers that they have in common are 1, 2, 3, and 6 • The greatest number is 6

  11. GCF try these: • 45 • 120 • 52 • 78 • 30 • 66

  12. 5.4 Understanding Fractions • Fractions are numbers that describe the division of a whole into equal parts. • Numerator – the parts being considered (the top number) • Denominator – the total number of equal parts or objects (the bottom number)

  13. 5.5 Equivalent Fractions • Fractions that have different numerators and denominators but name the same amount are called equivalent or equal • For instance 1/3 and 1/3 is the same as 2/3, 4/6, 6/9, 8/12 • You can either multiply or divide • MOST IMPORTANT – whatever you do to the numerator – you MUST do the exact same to the denominator in order for it to be equal

  14. 5.6 Simplest Form • To find the simplest form – Divide by the GCF of the numerator and denominator • Continue to divide until there is no other common number that can go into numerator and denominator besides 1 • Try these:

  15. Reminders: • Factors – start with 1 and number and CANNOT be bigger than the number • Multiples – Start with number and are the fact tables • Divisibility – use chart – must be able to DIVIDE out evenly • Prime number – only 1 and itself can evenly divide it • Composite number – any number that is not prime • Greatest Common Factor – the largest common factor of a set of numbers • You must BE FAIR whatever you do to numerator, you MUST do to denominator! • Equivalent – fractions that use different numbers but name same amount • Simplest form – a fraction divided down until nothing can divide it besides on

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