Horizons Math Sampler - Odyssey Academy
Horizons Math Sampler - Odyssey Academy
Horizons Math Sampler - Odyssey Academy
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<strong>Horizons</strong> <strong>Math</strong> 4 SAMPLE<br />
Prime Numbers<br />
Lesson 45<br />
Eratosthenes invented a way to find prime numbers long ago. Look at the<br />
instructions and table to see how it was done. If you would like to do this<br />
exercise yourself, use worksheet 25.<br />
1. 1 is not prime. Cross it out.<br />
2. Circle 2. Use skip counting to find all the numbers having 2 as a factor (4, 6, 8,<br />
10...). Cross out these numbers.<br />
3. Circle 3. Use skip counting to find all the numbers having 3 as a factor (3, 6, 9,<br />
12...). Cross out these numbers.<br />
4. Continue with 5, 7, 11, and so on. All the numbers not crossed out are prime.<br />
1 2 3 4 5 6 7 8 9 10<br />
11 12 13 14 15 16 17 18 19 20<br />
21 22 23 24 25 26 27 28 29 30<br />
31 32 33 34 35 36 37 38 39 40<br />
41 42 43 44 45 46 47 48 49 50<br />
The prime numbers less than 50: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, and 47.<br />
1<br />
Shade all prime numbers to find the MYSTERY message. (There are 21.)<br />
29 43 2 30 29 16 11<br />
13 10 3 40 13 3 20<br />
43 4 5 50 17 12 18<br />
23 8 7 22 31 47 12<br />
17 47 11 25 37 14 31<br />
43
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