Primes Factors and Common Factors Objective SWBAT find

Primes, Factors and Common Factors Objective: SWBAT find the primes of numbers, the factors of numbers and the common factors from a set of numbers.

Vocabulary Factors Prime Number Prime Factors numbers you can multiply together to get another number a number which only has two factors, 1 and itself a factor of a number which is also a prime number Highest Common Factor largest factor between two or more numbers

Rules of Divisibility: 2 – Any number that ends in an even number (0, 2, 4, 6, 8) in the ones place is divisible by 2. 3 – Add the digits across if you get (3, 6, 9, …) the number is divisible by 3. 5 – Any number that ends in a 0 or a 5 in the ones place is divisible by 5. 7 – If the above numbers (2, 3 & 5) don’t work try 7. If 2, 3, 5 & 7 don’t work the number is probably prime.

List all the factors of the following numbers and circle the prime factors. 1. 66 – 1, 2, 3, 6, 11, 22, 33, 66 2. 75 1, 3, 5, 15, 25, 75 3. 28 1, 2, 4, 7, 14, 28

Find the prime factors of the following numbers. Express each number as a product of prime numbers, using indices (exponents) when needed. (Hint: Use a factor tree. ) 4. 12 3 5. 4 2 64 8 2 Answer: 22 ∙ 3 2 8 4 2 2 2 4 2 Answer: 26 2

For each of these pairs of numbers: list the factors of each number, write down the common factors and then write down the highest common factor. 6. 14 1, 2, 7, 14 21 1, 3, 7, 21 Common Factors 1, 7 Highest Common Factor 7

For each of these pairs of numbers: list the factors of each number, write down the common factors and then write down the highest common factor. 7. 12 1, 2, 3, 4, 6, 12 36 1, 2, 3, 4, 6, 9, 12, 18, 36 Common Factors 1, 2, 3, 4, 6, 12 Highest Common Factor 12