Name
Date
DIRECTIONS: Cross out 1. Circle 2 and cross out its other multiples. Do the same for 3, 5 and 7. What is left is prime.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
| 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 |
| 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 |
| 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39 | 40 |
| 41 | 42 | 43 | 44 | 45 | 46 | 47 | 48 | 49 | 50 |
| 51 | 52 | 53 | 54 | 55 | 56 | 57 | 58 | 59 | 60 |
| 61 | 62 | 63 | 64 | 65 | 66 | 67 | 68 | 69 | 70 |
| 71 | 72 | 73 | 74 | 75 | 76 | 77 | 78 | 79 | 80 |
| 81 | 82 | 83 | 84 | 85 | 86 | 87 | 88 | 89 | 90 |
| 91 | 92 | 93 | 94 | 95 | 96 | 97 | 98 | 99 | 100 |
Done for you 1 crossed out · 2 circled ·
4, 6, 8, 10 crossed out (multiples of 2) — carry on with 12, 14, 16…
- How many primes are there under 100? Count the ones still standing.
- Look at the crossed-out numbers. Describe the pattern the multiples of 2 make on the chart, and the pattern the multiples of 5 make.
- 2 is the only even prime. Explain why there cannot be another one.
- Find two primes that differ by 2 — like 11 and 13. These are called twin primes. List three more pairs.
- Between 1 and 50 there are fifteen primes. Between 50 and 100 there are only ten. What does that suggest happens to primes as numbers get bigger?