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\\January 6, 2024 4:47 PM Surender Prajapati Proof 5 Reader _________________________ Date: ___________________74
We can observe from the table:
Numbers 2, 3, 5 and 7 have exactly two factors.
Numbers 4, 6, 8, 9 and 10 have more than two factors.
Thus, numbers which have only two factors, 1 and the number itself, are called prime
numbers and the numbers which have more than two factors are called composite
numbers.
Remember
Let us find prime and composite numbers between 1 and 100. A The number 1 is a
Greek mathematician, Eratosthenes, developed an interesting and unique number. It
simple method for this, which is why it is called the ''Sieve of is neither prime nor
composite.
Eratosthenes'.
activity
Step 1: Take a chart paper
and make a 10 × 1 2 3 4 5 6 7 8 9 10
10 grid and write 11 12 13 14 15 16 17 18 19 20
numbers from 1 to
100 in it. 21 22 23 24 25 26 27 28 29 30
Step 2: Colour the box of 1 as 31 32 33 34 35 36 37 38 39 40
it is a unique number. 41 42 43 44 45 46 47 48 49 50
Step 3: Circle the number 2
and cross out all its 51 52 53 54 55 56 57 58 59 60
multiples. 61 62 63 64 65 66 67 68 69 70
Step 4: Circle 3 and cross 71 72 73 74 75 76 77 78 79 80
out all its multiples.
(Some multiples of 3 81 82 83 84 85 86 87 88 89 90
may be cross out as 91 92 93 94 95 96 97 98 99 100
of multiples of 2.)
Step 5: Circle 5 and cross out all its multiples.
Step 6: Circle 7 and cross out all its multiples.
Step 7: Continue this process till all the numbers are either crossed out or circled.
All the circled numbers are prime numbers and all the crossed-out numbers are composite
numbers.
The prime numbers between 1 and 100 are 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41,
43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89 and 97.
Think and Answer
2 is the smallest and only even prime number. Is your roll number a prime
4 is the smallest composite number. number? Check.
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