Lesson 10. Factors and prime numbers

понедельник, 14 ноября 2016 г.

Lesson 10. Factors and prime numbers

A factors is a numbers which divides exactly into another numbers (there will be no remainder)

If 2 divides into a number exactly, that number is an even number (2, 4, 6, 8).

If 2 does not divide into a number exactly, that number is an odd number (1, 3, 5, 7).

A prime number can only be divide by to different numbers (these are the numbers 1 and itself). The first four prime numbers are 2, 3, 5, 7.

EXAMPLE:

All the factors of 10 are

1, 2, 5, 10.

Prime factors

Factors of a numbers which are also prime numbers are called prime factors. We can find these prime factors by using a 'factor tree' or by dividing by prime numbers again and again.

EXAMPLE:

Find the prime factors of 36.

METHOD 1:

Factor tree

Split into 4 and 9 because 4 × 9 = 36

Split 4 into 2 × 2

Split 9 into 3 × 3

Stop splitting when all numbers are prime numbers

We can say 36 = 2 × 2 × 3 × 3

METHOD 2:

Dividing by prime numbers

Dividing by any prime number

Stop when you get 1

These are prime factors.

We can say 36 = 2 × 2 × 3 × 3

The product of prime factors

When we write 36 = 2 × 2 × 3 × 3, the prime factors 2, 2, 3 and 3 are multiplied together. This is called a product.

2 × 2 × 3 × 3 is the product of its prime factors.

Index form

2 × 2 = 2² 3 × 3 = 3²

So 36 = 2 × 2 × 3 × 3

can be written as 2² × 3²

The answer written like this using power is said to be in index form.

Tasks to the lesson 10

Other lessons:

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понедельник, 14 ноября 2016 г.