In the fraction x/y, where x and y are positive integers, what is the value of y? The least common...
GMAT Data Sufficiency : (DS) Questions
In the fraction \(\frac{\mathrm{x}}{\mathrm{y}}\), where \(\mathrm{x}\) and \(\mathrm{y}\) are positive integers, what is the value of \(\mathrm{y}\)?
- The least common denominator of \(\frac{\mathrm{x}}{\mathrm{y}}\) and \(\frac{1}{3}\) is 6.
- \(\mathrm{x} = 1\)
Understanding the Question
We need to find the exact value of y in the fraction \(\mathrm{x/y}\), where both x and y are positive integers.
What We Need to Determine
For sufficiency, we must find exactly one specific value for y. If multiple values are possible, that's not sufficient for a "value" question.
Given Information
- \(\mathrm{x/y}\) is a fraction
- Both x and y are positive integers
- We need the specific value of y
Analyzing Statement 1
Statement 1: The least common denominator of \(\mathrm{x/y}\) and \(\mathrm{1/3}\) is 6.
Let's understand what this means. The LCD of two fractions is the smallest number that both denominators divide into evenly.
Here's the key insight: Since LCD = 6 and we know \(\mathrm{6 = 2 \times 3}\), let's think about what this tells us:
- The fraction \(\mathrm{1/3}\) already has denominator 3
- For the LCD to be 6 (not just 3), the denominator y must contribute the factor 2
- This means y must be divisible by 2
But wait—which multiples of 2 give us LCD = 6?
- If y = 2: \(\mathrm{LCD(2, 3) = 6}\) ✓ (Works!)
- If y = 4: \(\mathrm{LCD(4, 3) = 12 \neq 6}\) (Too large)
- If y = 6: \(\mathrm{LCD(6, 3) = 6}\) ✓ (Also works!)
So y could be either 2 or 6. Since we have two possible values, Statement 1 is NOT sufficient.
[STOP - Not Sufficient!] This eliminates choices A and D.
Analyzing Statement 2
Now let's forget Statement 1 completely and analyze Statement 2 independently.
Statement 2: x = 1
This tells us our fraction becomes \(\mathrm{1/y}\). But knowing that x = 1 tells us nothing about y. Since y can be any positive integer (1, 2, 3, 4, ...), we have infinitely many possibilities.
Statement 2 is NOT sufficient.
[STOP - Not Sufficient!] This eliminates choices B and D (already eliminated).
Combining Statements
Now let's use both statements together:
- From Statement 1: y must be either 2 or 6
- From Statement 2: x = 1
This gives us the fraction \(\mathrm{1/y}\) where y is either 2 or 6. So our fraction could be:
- \(\mathrm{1/2}\), or
- \(\mathrm{1/6}\)
Even with both pieces of information, we still cannot determine which specific value y takes.
The statements together are NOT sufficient.
[STOP - Not Sufficient!] This eliminates choices C (and A, B, D already eliminated).
The Answer: E
Since neither statement alone nor both statements together allow us to determine a unique value for y, the answer is E.
Answer Choice E: "The statements together are not sufficient."