### Brain Teasers

# Sophie

Group
These brain teasers rely on your ability to recognize groups of common attributes. For each of these puzzles you'll need to figure out why the words or letters are grouped as they are. Sometimes you will be asked to pick the odd-one-out or to place a new word into the correct group.

Which number doesn't belong and why?

23, 41, 89, 11, 43, 131

23, 41, 89, 11, 43, 131

### Hint

1. Notice they are all prime numbers.2. The title is a hint.

### Answer

43 because the rest are Sophie Germain primes. Sophie Germain primes are prime numbers where if you multiply it by 2 and add 1, you still have a prime number.23*2+1=47

41*2+1=83

89*2+1=179

11*2+1=23

131*2+1=263

but

43*2+1=87

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