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E:\Working\Focus_Learning\Math_Genius_5_(05-10-2023)\Open_Files\CHAP_03
\\February 16, 2024 2:20 PM Surender Prajapati Proof 5 Reader _________________________ Date: ___________________74
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.
Let us find prime and composite numbers between 1 and 100.
Remember
A Greek mathematician, Eratosthenes, developed an interesting The number 1 is a
and simple method for this, which is why it is called the ''Sieve of unique number. It
is neither prime nor
Eratosthenes'. composite.
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: Enclose 1 in a box 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.
2 is the smallest and only even prime number. Think and Answer
Is your roll number a prime
4 is the smallest composite number. number? Check.
Mathematics-5 65
