Prime number puzzles

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Learn it Know the primes under 100: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97. 2 is the only even prime.

Example: Write 30 as a sum of two primes in every possible way.

Try each prime up to 15: 30 − 7 = 23 ✓, 30 − 11 = 19 ✓, 30 − 13 = 17 ✓.
30 − 2 = 28, 30 − 3 = 27, 30 − 5 = 25 are not prime.
3 ways: 7 + 23, 11 + 19, 13 + 17.

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