by 
Owl Zero
ANSWERS: 2
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11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97 i guess there are 21 two digit prime numbers..
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There are some who would say "all but 2,3,5 and 7", since all the rest have at least two digits. Otherwise here is how to find the primes up to 100 Imagine the numbers from 2-100. The first number is the first prime. Cross out all multiples of 2. Now you have odd numbers. Write them down. The first number is the next prime 3. Now cross out numbers divisible by 3. The first number left is the next prime 5. Cross out numbers divisible by 5. Here is what is left so far: 7 11 13 17 19 23 29 31 37 41 43 47 49 53 59 61 67 71 73 77 79 83 89 91 97 7 is the next prime, cross out numbers divisible by 7, the second one to cross out after the 7 will be 7*7 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97 The next prime is 11. The second one to cross out after the 11 will be 121 so now we can stop. This is called the Sieve of Eratosthenes
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