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In a locker room each row of lockers has the same number of lockers, and the number of rows is...

GMAT Data Sufficiency : (DS) Questions

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In a locker room each row of lockers has the same number of lockers, and the number of rows is \(\frac{1}{2}\) the number of lockers in a row. How many lockers are in a row?

  1. There is a total of 72 lockers in the locker room.
  2. In the locker room, the number of rows is 6 less than the number of lockers in a row.
A
Statement (1) ALONE is sufficient but statement (2) ALONE is not sufficient.
B
Statement (2) ALONE is sufficient but statement (1) ALONE is not sufficient.
C
BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D
EACH statement ALONE is sufficient.
E
Statements (1) and (2) TOGETHER are not sufficient.
Solution

Understanding the Question

Let's break down what we're dealing with in this locker room setup:

  • Every row has exactly the same number of lockers
  • The number of rows equals exactly half the number of lockers in each row

If we call the number of lockers in a row "L", then we have L/2 rows. This creates a special relationship:
Total lockers = \(\mathrm{L} \times (\mathrm{L}/2) = \mathrm{L}^2/2\)

What we need to find: The exact value of L (number of lockers in a row).

Key insight: Since the total must equal \(\mathrm{L}^2/2\), this means the total number of lockers must be half of a perfect square. This pattern recognition will guide our entire analysis.

Analyzing Statement 1

Statement 1: There are 72 lockers total in the locker room.

Using our insight, we know that total = \(\mathrm{L}^2/2\), so:

  • \(\mathrm{L}^2/2 = 72\)
  • Therefore, \(\mathrm{L}^2 = 144\)

Now we need to find which perfect square equals 144. Since \(12 \times 12 = 144\), we know L = 12.

Quick verification:

  • 12 lockers per row
  • \(12/2 = 6\) rows
  • Total: \(12 \times 6 = 72\)

This gives us exactly one value for L.

[STOP - Statement 1 is SUFFICIENT!]

This eliminates choices B, C, and E.

Analyzing Statement 2

Now let's forget Statement 1 completely and analyze Statement 2 independently.

Statement 2: The number of rows is 6 less than the number of lockers in a row.

From the question setup, we know:

  • Number of rows = \(\mathrm{L}/2\)

Statement 2 tells us:

  • Number of rows = L - 6

Since both expressions equal the number of rows:
\(\mathrm{L}/2 = \mathrm{L} - 6\)

Let's think strategically: We need a number where half of it equals the number minus 6.

Testing L = 12:

  • Half of 12 = 6
  • 12 minus 6 = 6
  • These match! ✓

Is this the only value? Yes - you can verify that L = 12 is the unique solution to this relationship.

[STOP - Statement 2 is SUFFICIENT!]

This eliminates choice C (and confirms our answer isn't A).

The Answer

Both statements independently lead us to the exact same answer: 12 lockers per row.

  • Statement 1 alone → L = 12
  • Statement 2 alone → L = 12

Since each statement alone is sufficient to answer the question:

Answer: D - Each statement alone is sufficient.

Answer Choices Explained
A
Statement (1) ALONE is sufficient but statement (2) ALONE is not sufficient.
B
Statement (2) ALONE is sufficient but statement (1) ALONE is not sufficient.
C
BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D
EACH statement ALONE is sufficient.
E
Statements (1) and (2) TOGETHER are not sufficient.
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