Three Primes

Given that p , p + 10 , p + 14 p , p+10 , p+14 are prime numbers , find the number of all possible values of p p .


The answer is 1.

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2 solutions

Maggie Miller
Aug 28, 2015

Note modulo 3 3 , p + 10 p + 1 , p + 14 p + 2 p+10\equiv p+1, p+14\equiv p+2 . Therefore, one of p , p + 10 , p + 14 p,p+10,p+14 is divisible by 3 3 . Since each number is prime, we conclude one of p , p + 10 , p + 14 p, p+10,p+14 is equal to 3 3 . Since p p is positive, we must have p = 3 p=3 .

We easily verify that p = 3 p=3 does in fact yield 3 3 prime numbers (namely 3 , 13 , 17 3,13,17 ). Therefore, there is one such value of p p , so the answer is 1 \boxed{1} .

Wow nice explanation

Ishita .S - 5 years, 9 months ago
Mr Yovan
Aug 29, 2015

As p+10 and p+14 are prime numbers,they cannot be divisible by 3,so the sum of their digits cannot be a multiple of 3,so p cannot has his sum equal to 2 otherwise the sum of digits of p+10 would be a multiple of 3,and its sum of digits cannot be neither 2,5,8,11... P cannot has the sum of digits equal to 1 otherwise p +14 would be a multiple of 3.p cannot has the sum equal to 1,4,7,10... Therefore the sum of digits of p can only be 3,6,9....but if the sum of digits of p is equal to such a multiple of 3 p wouldn't be prime,except if p is 3 Therefore p can only be 3 Sorry by my english errors,i am br,hu3hu3 gibe money and points

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