Multiples and factors. Prime numbers First and Second Year of Secondary Education

 The Sieve of Erathostenes. The Sieve of Erathostenes is a procedure to find the first prime numbers. - Draw a table with the natural numbers starting with 2. This table is usually filled with the first hundred natural numbers, but here it only goes up to the number 46. - Start with the number 2, leave it, but from there, count by twos and drag out the numbers that are multiples of 2. - The first of the remaining numbers is 3, leave it and from 3, drag out all the numbers that are multiples of 3. - The next of the remaining numbers is 5, leave it and from 5, drag out the numbers thar are multiples of 5. - Go on and every time you get to a number that has not been dragged out, leave it, but from there, drag out all the numbers that are multiples of it. Continue, right to the end. - Finally, only prime numbers are left. Esta unidad interactiva requiere la máquina virtual de Java J2RE.

 Eduardo Barbero Corral Spanish Ministry of Education. Year 2007