Prince1890Sharma
Given a sequence of 58 terms; such that each term has the form P + n where P stands for the product 2 × 3 × 5 …× 61 of all prime numbers less than or equal to 61, and ‘n’ takes, successively, the values 2, 3, 4, …, 59. If M is the number of primes appearing in this sequence, then what is the value of M?
(A) 0
(B) 16
(C) 17
(D) 57
(E) 58
Hello
Bunuel, Can you please provide the explanation to this question?
The sequence will be:
2 × 3 × 5 …× 61 + 2 = 2(1 × 3 × 5 …× 61 + 1)
2 × 3 × 5 …× 61 + 3 = 3(2 ×1 × 5 …× 61 + 1)
2 × 3 × 5 …× 61 + 4 = 2(1 × 3 × 5 …× 61 + 2)
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2 × 3 × 5 …× 61 + 58 = 2(1 × 3 × 5 …× 61 + 29)
2 × 3 × 5 …× 61 + 59 = 59(2 × 3 × 5 …× 1 × 61 + 1)
Observe that since 2 × 3 × 5 …× 61 is the product of all the primes from 2 to 61, inclusive, from each term we were able to factor out a prime both from the first term, 2 × 3 × 5 …× 61, as well as from the second term, 2, 3, 4, ..., 59. Hence, each term will be represnted as the product of two numbers each of which is greater than 1. Hence, none of the terms is prime.
Answer: A.