Showing posts with label prime numbers. Show all posts
Showing posts with label prime numbers. Show all posts

Tuesday, May 27, 2014

How to find gcd (greatest common divisor)


The divisor of a number is a natural number that divides another, and which results in an integer. For example, the dividers of 12 are 1, 2 , 3, 4, 6 and 12. Set of divisors of a number is always a finite set of numbers.

12: 1 = 12
12: 2 = 6
12: 4 = 3
12: 4 = 3
12 6 = 2
12: 12 = 1

D12 = { 1,2,3,4,6,12 }

The gcd (greatest common divisor), as the name implies, is the greatest common divisor of two or more numbers integers. For example, if D12 = { 1,2,3,4,6,12 } and D18 = { 1,2,3,6,9,18 }, the greatest common divisor between 12 and 18 is 6. Yet, if instead of making the gcd of 12 and 18, we do the gcd of two much larger numbers, it will take too long. Thus, instead of making the dividers of each number, there is a faster method.


Now we'll explain how to do the gcd of two or more numbers integers.


Step 1

By making the decomposition in prime factors of each number. If you don't know how to decompose a number into prime factors, click here.


Step 2

After you've decompose down each number into its prime factors, you will choose the smallest common factors. The non common factores doesnt interest.


Step 3

Calculates the product of the selected factors . The result is the greatest common divisor of the two given numbers integers.

Tuesday, March 18, 2014

How to do prime factorization

The Fundamental Theorem of Arithmetic states that any composite number (number divisible by more than two dividers) , is a product of prime numbers. So, in this article you will learn how to do prime factorization. This decomposition will allow then calculate the lcm (least common multiple) and gcd (greatest common divisor).


Prime Factorization method

With this two examples we will explain how to make the prime factorization (decomposition into prime factors).

decompose a composite number in prime numbers


Taking one of the examples :

- Check if the number is divisible by the first prime number, 2. If so, perform the division (12: 2 = 6). If not, see if it is divisible by the following prime number, and so on, until you find a prime number that is a divisor of the given number. To do this step is important to know the divisibility rules.

- Repeat the same procedure until you have the result 1.

- The number you want to decompose is the product of all prime numbers placed to the right of the line.


The tree method

In this method of prime factorization, you will decompose the given number, until you have only prime numbers. Look at the example. 

tree method


We hope that this article was helpfull to you learn how to do prime factorization and study maths.

Friday, March 14, 2014

Prime numbers up to 100

Do you know what is a prime number? To help you understand what is this special number and to use them to study maths, below you can find the definition of prime numbers and the first prime numbers up to 100.


The simplest definition is that a prime number is a number that is only divisible by itself and 1. That is, it has two dividers. For this reason, it is not considered the number 1 to be a prime number. All the numbers that have more than two dividers are called composite numbers. 


For example, the set of dividers of the number 5 is {1,5}, then 5 is a prime number. 


There are an infinite number of primes. Below are the prime numbers up to 100. 


List of the prime numbers up to 100: 

2, 3, 5, 7, 
11, 13, 17, 19, 
23, 29, 
31, 37, 
41, 43, 47, 
53, 59, 
61, 67, 
71, 73, 79, 
83, 89, 
97