Finding 4 Prime Numbers Less Than 50

Question

Seeking help identifying 4 prime numbers less than 50 that share this property: When a "1" is inserted anywhere, including the beginning and end, the new number is also prime.

Answer 1

Start with the primes less than 50:

1, 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47

Now add a 1 and eliminate the numbers that are no longer primes:

11, 12, 13, 15, 17, 111, 113

So the prime numbers that meet the criteria are 1, 3, 7, and 13