Question 1068751: A prime-prime is a prime number that yields a prime when its units digit is omitted. (For example, 317 is a three-digit prime-prime because 317 is prime and 31 is prime). How many two-digit prime-prime
are there? (Recall that 1 is not a prime number.)
Answer by ankor@dixie-net.com(22740)   (Show Source):
You can put this solution on YOUR website! A prime-prime is a prime number that yields a prime when its units digit is omitted.
(For example, 317 is a three-digit prime-prime because 317 is prime and 31 is prime).
How many two-digit prime-prime are there?
:
Find the prime numbers from 11 to 99, (2 is a prime number)
13 17 19 23 29 31 37 41 43 47 53 59 61 67
71 73 79 83 89 97
We can eliminate the teens, the 40's, the 60's, the 80's and the 90's, so we have
23, 29, 31, 37, 53, 59, 71, 73, 79
there are 9 prime-prime numbers
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