# Prime and Composite Numbers

 Sieve of Eratosthenes. Follow these steps: Step 1: Starting from the first number select the numbers divisible by 2 and choose "div by 2" in the drop box. Step 2: Among the remaining numbers select the numbers divisible by 3 and choose "div by 3" in the drop box. Step 3: Continue for numbers divisible by 5 and 7. Remember to work only on the remaining unselected numbers each time. Step 4: The numbers that finally remain unselected (left behind) are the prime numbers of the group.

Write them in order, in the text boxes below.

 15 Selectdiv by 2div by 5div by 7left behinddiv by 3 16  Selectdiv by 2div by 3div by 5div by 7 17  Selectdiv by 3div by 5left behind 18 Selectdiv by 2div by 3div by 5div by 7 19 Selectdiv by 2div by 3left behind 20 Selectdiv by 2div by 3div by 5div by 7left behind! 21 Selectdiv by 2div by 3div by 5left behinddiv by 3 22 Selectdiv by 2div by 3div by 5div by 7 23 Selectdiv by 2div by 3left behind 24 Selectdiv by 2div by 3div by 5div by 7

The prime numbers between 15 and 25 ⇒    ,  and

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