Question

If sequence S has 120 terms, what is the 105th term of S?
(1) The first term of S is -8.
(2) Each term of S after the first term is 10 more than the preceding term.

• A. Statement I alone is sufficient to answer the problem.
• B. Statement II alone is sufficient to answer the problem
• C. Statement I and II both are needed.
• D. Either of the Statements I or II is sufficient alone.
• E. Statement I and II both are not sufficient.

Answer 1

Answer: (C)

Statement I and II both are needed.

Arithmetic Sequences

This problem can be solved by determining at least one term of the sequence and how each term is derived from the preceding term (s).

(1) This indicates that the first term of the sequence is -8, but does not indicate how subsequent terms are derived; NOT sufficient.

(2) This indicates how each term is derived from the preceding term, but does not indicate at least one term of the sequence; NOT sufficient.

Taking (1) and (2) together, the first term is -8 and each subsequent term is 10 more than the preceding term from which the 105th term can be determined.

The correct answer is C; both statements together are sufficient.