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P. 64
Worksheet
Sieve of Eratosthenes
Let’s learn to find prime numbers from 1 to 100 using the Sieve of Eratosthenes method
founded by the Greek mathematician Eratosthenes in the third century BC.
1. Write the remaining numbers from 11 to 100 1 2 3 4 5 6 7 8 9 10
in the adjacent grid in a row format.
2. Cross out 1 as it is not a prime number.
3. Encircle the first prime number, i.e., 2.
4. Cross out all the multiples of 2.
5. Encircle the next uncrossed number i.e., 3 and
cross out all its multiples.
6. Encircle the next uncrossed number, i.e., 5
and cross out all its multiples.
7. Encircle the next uncrossed number, i.e., 7
and cross out all its multiples.
8. Continue this procedure till all the numbers
from 1 to 100 are either encircled or crossed out.
9. The encircled numbers are prime numbers from 1 to 100.
Prime numbers from 1 to 100 are 2, 3, 5, 7, ___________________________________
________________________________________________________________________
_______________________.
10. Crossed out numbers except 1 are composite numbers.
Composite numbers from 1 to 100 are 4, 6, 8, 9, 10, ____________________________
________________________________________________________________________
__________________________.
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