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Farm Dog

Trick brain teasers appear difficult at first, but they have a trick that makes them really easy.

 

Puzzle ID:#25004
Fun:** (2.05)
Difficulty:*** (2.86)
Category:Trick
Submitted By:cnmne*us*****

 

 

 



The numbers 2 and 5 are the only two prime numbers that end in 2 or 5. What is the rationale for the following groups of numbers?

3 17 31 47 61
7 19 37 49 67
11 23 41 53 71
13 29 43 59 73




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