Question: Number of Primes

Comment on Number of Primes

Really, it's better to learn the prime numbers up to 97, right?
greenlight-admin's picture

The more primes the better :-)

Nice solution. Could you please tell me in which lesson did you explain that, if the addition of to digits is 15, then that number is divisible by 3. I mean the case for 87 how to know that is divisible by 3?.

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