If Bob produces 36 or fewer items in a week, he is paid X dollars per item. If Bob produces...
GMAT Data Sufficiency : (DS) Questions
If Bob produces \(36\) or fewer items in a week, he is paid \(\mathrm{X}\) dollars per item. If Bob produces more than \(36\) items in a week, he is paid \(\mathrm{X}\) dollars per item for the first \(36\) items and \(\frac{3}{2}\) times that amount for each additional item. How many items did Bob produce last week?
- Last week Bob was paid total of \($480\) for the items that he produced that week.
- This week Bob produced \(2\) items more than last week and was paid a total of \($510\) for the items that he produced this week.
Understanding the Question
What We Need to Determine
We need to find the exact number of items Bob produced last week. This is a value question - we need a single, specific number.
Given Information
- If Bob produces \(≤36\) items: He earns X dollars per item
- If Bob produces \(>36\) items: He earns X dollars for the first 36 items, then 1.5X dollars for each additional item
- There's a payment threshold at 36 items where overtime kicks in
Key Insight
The payment structure creates a "jump" at 36 items. This means the same total payment could potentially come from different production levels - either fewer items at a higher base rate, or more items at a lower base rate (with overtime compensation). This insight will guide our analysis throughout.
Analyzing Statement 1
Statement 1 tells us: Last week Bob was paid $480 total.
Testing Different Scenarios
Let's see if different base rates (X) could lead to different production quantities:
Scenario 1: What if Bob produced 32 items (below threshold)?
- If X = $15 per item: \(32 × \$15 = \$480\) ✓
- This works!
Scenario 2: What if Bob produced more than 36 items?
- If X = $10 per item, with overtime at $15:
- First 36 items: \(36 × \$10 = \$360\)
- Additional items needed: \((\$480 - \$360) ÷ \$15 = 8\) items
- Total items: \(36 + 8 = 44\) items ✓
- This also works!
Conclusion
Since we found two different production quantities (32 items and 44 items) that both result in $480 payment, we cannot determine a unique answer.
Statement 1 is NOT sufficient.
Analyzing Statement 2
Now let's forget Statement 1 completely and analyze Statement 2 independently.
Statement 2 tells us: This week Bob produced 2 more items than last week and was paid $510.
What This Reveals
We know:
- Last week: n items (unknown)
- This week: \(\mathrm{n} + 2\) items, paid $510
- The payment increased by some amount for 2 additional items
Testing Different Scenarios
The key insight is that we don't know whether Bob is working below or above the 36-item threshold:
Scenario 1: Both weeks below 36 items
- If n = 30 last week, then 32 items this week
- Each item pays the same rate X
- We'd need \(32\mathrm{X} = \$510\), so \(\mathrm{X} ≈ \$15.94\)
- This is possible!
Scenario 2: Both weeks above 36 items
- If n = 40 last week, then 42 items this week
- Both additional items earn overtime rate \(1.5\mathrm{X}\)
- Different values of n and X could satisfy this
- This is also possible!
Without knowing which scenario we're in or the value of X, we cannot determine n uniquely.
Statement 2 is NOT sufficient.
Combining Statements
Combined Information
From both statements together:
- Last week: n items, paid $480
- This week: \(\mathrm{n} + 2\) items, paid $510
- Payment increased by exactly $30 for 2 additional items
The Critical Insight
The $30 increase for 2 items averages to $15 per item. This is crucial - this $15/item could represent:
Case 1: Both weeks below threshold \((\mathrm{n} ≤ 34)\)
- Each item pays the base rate X
- If \(\mathrm{X} = \$15\): Last week 32 items ($480), this week 34 items ($510) ✓
Case 2: Both weeks above threshold \((\mathrm{n} > 36)\)
- Additional items pay overtime rate \(1.5\mathrm{X}\)
- If overtime rate = $15, then base rate \(\mathrm{X} = \$10\)
- With \(\mathrm{X} = \$10\): We can verify that \(\mathrm{n} = 44\) items also satisfies both conditions ✓
Why Multiple Solutions Exist
The payment structure allows the same payment increase ($15/item) to occur at different production levels - either as the base rate below the threshold or as the overtime rate above it. Since we've found two different values \((\mathrm{n} = 32\) and \(\mathrm{n} = 44)\) that satisfy both statements, the combined information still doesn't give us a unique answer.
The statements together are NOT sufficient.
The Answer: E
Even with both pieces of information, we cannot uniquely determine how many items Bob produced last week because the payment structure allows multiple valid scenarios.
Answer Choice E: "The statements together are not sufficient."