Intensive classes for GMAT in Madras, Bombay and Bangalore in India. Weekend & Weekday classes. Includes study material and tests. Tutors include 98%ilers in GMAT & ISB / IIM Graduates.

You are here: Home » GMAT Test Prep Questions » Arithmetic and Geometric Progressions » Question 7

The GMAT DS question given below is from the topic Arithmetic Progressions. Problems on Arithmetic Progressions are quite easy if one understands that the basic concept behind AP is just an extrapolation of simple multiplication tables.

Directions

This data sufficiency problem consists of a question and two statements, labeled (1) and (2), in which certain data are given. You have to decide whether the data given in the statements are sufficient for answering the question. Using the data given in the statements, plus your knowledge of mathematics and everyday facts (such as the number of days in a leap year or the meaning of the word counterclockwise), you must indicate whether -

1. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient to answer the question asked.
2. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient to answer the question asked.
3. BOTH statements (1) and (2) TOGETHER are sufficient to answer the question asked, but NEITHER statement ALONE is sufficient to answer the question asked.
4. EACH statement ALONE is sufficient to answer the question asked.
5. Statements (1) and (2) TOGETHER are NOT sufficient to answer the question asked, and additional data specific to the problem are needed.

Numbers
All numbers used are real numbers.

Figures
A figure accompanying a data sufficiency question will conform to the information given in the question but will not necessarily conform to the additional information given in statements (1) and (2).

Lines shown as straight can be assumed to be straight and lines that appear jagged can also be assumed to be straight.

You may assume that the positions of points, angles, regions, etc. exist in the order shown and that angle measures are greater than zero.

All figures lie in a plane unless otherwise indicated.

Note
In data sufficiency problems that ask for the value of a quantity, the data given in the statement are sufficient only when it is possible to determine exactly one numerical value for the quantity.

A set S contains the following elements: {7, 11, 15, 19, 23, x}. What is the value of x?
(1)    The elements are in arithmetic progression
(2)    x is prime

The correct choice is (C). Statements (1) and (2) Taken TOGETHER are sufficient to answer the question asked.

Statement 1 : The elements are in arithmetic progression.

So, x could either be 3 or 27.

INSUFFICIENT.

Statement 2 : x is prime

x could be any prime number.

INSUFFICIENT

Combining the two statements, we know that x could take only two values from statement 1. viz., 3 or 27; from statement 2 we know that x is prime. 3 is the only value that satisfies both the conditions.

Hence, choice(C) is the correct answer.

---

More Questions in Sequences & Series : AP GP

1. Sum of all 3 digit numbers leaving remainder ..	2. Number of 3 digit numbers leaving remainder ..
3. 9th term of an arithmetic sequence	4. Sum of 1st 15 terms given 4th plus 12th term
5. Given sum of geometric progression; find r.	6. Sum of 2 sets of even numbers.
7. DS : Finding x, a missing term in an AP.	8. Finding number of terms of an AP.
9. DS : Finding the 6th term of an AP.	10.