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Prime numbers
The sieve of Eratosthenes is one of a number of prime number sieves,
and ancient algorithm for finding all prime numbers by marking the
multiples of each prime, starting with the multiples of 2.
Find all the prime numbers between 1 and 50 using Eratosthenes’
method.
⑴ List all the consecutive integers from 1 to 50.
⑵ M ark on 1 as it is not a prime number. Mark on all the multiples of
2 except the number 2 as it is a prime number.
⑶ Mark on all the multiples of 3 except the number 3 as it is a prime
number.
⑷ Mark on all the multiples of 5 except the number 5 as it is a prime number.
⑸ Mark on all the multiples of prime numbers except the prime numbers
of the remaining numbers.
⑹ All the numbers in the list that are not marked are prime numbers.
1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20 11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30 21 22 23 24 25 26 27 28 29 30
31 32 33 34 35 36 37 38 39 40 31 32 33 34 35 36 37 38 39 40
41 42 43 44 45 46 47 48 49 50 41 42 43 44 45 46 47 48 49 50
⑵ ⑶
1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20 11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30 21 22 23 24 25 26 27 28 29 30
31 32 33 34 35 36 37 38 39 40 31 32 33 34 35 36 37 38 39 40
41 42 43 44 45 46 47 48 49 50 41 42 43 44 45 46 47 48 49 50
⑸ ⑷
< Prime numbers between 1 and 50 >
2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47
40 Workbook S-4
The sieve of Eratosthenes is one of a number of prime number sieves,
and ancient algorithm for finding all prime numbers by marking the
multiples of each prime, starting with the multiples of 2.
Find all the prime numbers between 1 and 50 using Eratosthenes’
method.
⑴ List all the consecutive integers from 1 to 50.
⑵ M ark on 1 as it is not a prime number. Mark on all the multiples of
2 except the number 2 as it is a prime number.
⑶ Mark on all the multiples of 3 except the number 3 as it is a prime
number.
⑷ Mark on all the multiples of 5 except the number 5 as it is a prime number.
⑸ Mark on all the multiples of prime numbers except the prime numbers
of the remaining numbers.
⑹ All the numbers in the list that are not marked are prime numbers.
1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20 11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30 21 22 23 24 25 26 27 28 29 30
31 32 33 34 35 36 37 38 39 40 31 32 33 34 35 36 37 38 39 40
41 42 43 44 45 46 47 48 49 50 41 42 43 44 45 46 47 48 49 50
⑵ ⑶
1 2 3 4 5 6 7 8 9 10 1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20 11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30 21 22 23 24 25 26 27 28 29 30
31 32 33 34 35 36 37 38 39 40 31 32 33 34 35 36 37 38 39 40
41 42 43 44 45 46 47 48 49 50 41 42 43 44 45 46 47 48 49 50
⑸ ⑷
< Prime numbers between 1 and 50 >
2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47
40 Workbook S-4
