Multiple choice

n is a natural number and a(n) + 1 = a (n) + 5. Is a (50) - 1 divisible by 5? 1) a (1) = 3 2) a (49) is not divisible by 5

  1. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.

  2. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.

  3. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.

  4. EACH statement ALONE is sufficient.

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A Correct answer
Explanation

1) only, a (50) = a (49) + 5 = a (48) + 5 + 5 = a (48) + 2*5 =…= a (1) + 49*5 = 3 + 49*5, so a (50) - 1 = 49*5 + 2, which cannot be divisible by 5, sufficient. 2) only, a (50) = a(49) + 5, if a (49) is not divisible by 5, then a(50) must not be divisible by 5, but a (50) - 1 might be divisible by 5. Because we don't know the remainder of a(50) divided by 5, we don't know if a (50) - 1 can be divisible by 5 or not, insufficient.

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