Page 196 - New Medley 4 Semester 1

C. Find the smallest number that can be added to the encircled number
so that the sum is divisible by the number given in the box.

1. 422 3 2. 393 5 3. 736 10

4. 431 2 5. 746 3 6. 4251 5

D. 1. Write the numbers which lie between 30 and 50 and are divisible by
both 2 and 3.

2. Is every number divisible by 5 also divisible by 10? Give two examples
in support of your answer.

PROJECT WORK • Flexibility and Adaptability

Eratosthenes was a Greek mathematician.

He is well known for the sieve of Eratosthenes.

Find out more about him from the internet and other resources.
Let us also make the 100 – number chart he had prepared and answer the

questions that follow.
The Sieve of Eratosthenes

Z Z Take a 10 × 10 square grid
and write the numbers from 1 2 3 4 5 6 7 8 9 10
1 to 100. Leave 1 as it is
11 12 13 14 15 16 17 18 19 20
neither prime nor composite.

Z Z Encircle 2 and cross out all 21 22 23 24 25 26 27 28 29 30
other multiples of 2.
31 32 33 34 35 36 37 38 39 40
Z Z Encircle the next uncrossed
number, i.e., 3 and cross 41 42 43 44 45 46 47 48 49 50

out all other multiples of 3.
51 52 53 54 55 56 57 58 59 60
Z Z Encircle the next uncrossed
number, i.e., 5 and cross
61 62 63 64 65 66 67 68 69 70
out all other multiples of 5.

Z Z Encircle the next uncrossed 71 72 73 74 75 76 77 78 79 80
number, i.e., 7 and cross
81 82 83 84 85 86 87 88 89 90
out all other multiples of 7.

91 92 93 94 95 96 97 98 99 100
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