A prime number is called a '' Superprime '', if ; '' doubling it , and then subtracting 1 ,results - Maths - Integers

Question

A prime number is called a '' Superprime '', if ; '' doubling it ,
and then subtracting 1 ,results in another prime number" The number
of Superprimes less than 15 are: What is Superprime number? (1)2
(2) 3 (3) 4 (4) 5

Rishabh Mittal · Accepted Answer

Dear Student ,

Please find below the solution to the asked query :

2×2-1=3 , which is prime numberSo , 2 is superprime number 
2×3-1=5 , which is prime numberSo , 3 is superprime number 
2×5-1=9 , which is not a prime numberSo , 5 is not a superprime number 
2×7-1=13 , which is prime numberSo , 7 is superprime number 
2×11-1=21 , which is not a prime numberSo , 11 is not a superprime number 
2×13-1=25 , which is not a prime numberSo , 13 is not a superprime number 
So there are 3 superprime numbers less than 15 
Correct answer is 2 3 
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A prime number is called a '' Superprime '', if ; '' doubling it , and then subtracting 1 ,results in another prime number". The number of Superprimes less than 15 are: What is Superprime number? (1)2 (2) 3 (3) 4 (4) 5