Read the following statements and conclusions: Statements: Some hills are rivers. Some rivers are deserts. All deserts are roads. Conclusions: 1. Some roads are rivers. 2. Some roads are hills. 3. Some deserts are hills. Which of the above conclusions logically follow from the given statements?

Difficulty: Medium

Correct Answer: Only conclusion 1 follows.

Explanation:


Introduction / Context:
This syllogism question connects hills, rivers, deserts and roads. You must determine which conclusions about overlaps between these sets definitely follow from the given statements. It is a test of multi step reasoning with one "all" statement and two "some" statements.


Given Data / Assumptions:


    • Statement 1: Some hills are rivers. (H ∩ R ≠ ∅.)

    • Statement 2: Some rivers are deserts. (R ∩ D ≠ ∅.)

    • Statement 3: All deserts are roads. (D ⊆ Ro, where Ro is the set of roads.)

    • Conclusion 1: Some roads are rivers.

    • Conclusion 2: Some roads are hills.

    • Conclusion 3: Some deserts are hills.


Concept / Approach:
We use basic set relationships. When "all deserts are roads", everything in D is also in Ro. When "some rivers are deserts", there is at least one element in the intersection of R and D. Combining these, that element is simultaneously a river and a road. The more delicate question is whether hills must overlap with deserts or with roads, which requires extra care.


Step-by-Step Solution:
Step 1: Combine Statement 2 and Statement 3. Some rivers are deserts (R ∩ D ≠ ∅), and all deserts are roads (D ⊆ Ro). Therefore, at least one object is both a river and a desert, and that desert is also a road. Thus, there is at least one object that is both a river and a road. This directly supports Conclusion 1: Some roads are rivers. Step 2: Evaluate Conclusion 2: "Some roads are hills." We know: • Some hills are rivers (H ∩ R ≠ ∅). • Some rivers are deserts, and deserts are roads. However, the hills that are rivers might not be the same rivers that are deserts (and thus roads). It is quite possible that the river which is also a desert (and so a road) is not a hill, and the river which is a hill is not a desert. In that scenario, no hill is a road, so Conclusion 2 does not necessarily follow. Step 3: Evaluate Conclusion 3: "Some deserts are hills." For this to follow, D ∩ H must be non empty. But again, nothing in the statements requires that the specific deserts we know (which are also rivers and roads) are hills. Deserts might be a subset of rivers disjoint from the subset of rivers that are hills. Hence, we cannot guarantee that any desert is also a hill, so Conclusion 3 does not follow.


Verification / Alternative check:
Draw a diagram where: • One region is H ∩ R containing at least one hill river, • Another separate region is R ∩ D containing at least one river desert, • And D is entirely inside Ro (roads). Ensure that these two regions do not overlap. Then: • Some hills are rivers (true), • Some rivers are deserts (true), • All deserts are roads (true), but no road is a hill and no desert is a hill. In this model, only Conclusion 1 holds, while Conclusions 2 and 3 fail. Since such a model exists, only Conclusion 1 is logically necessary.


Why Other Options Are Wrong:
Option A is wrong because it ignores the clear chain from deserts to roads and from rivers to deserts that supports Conclusion 1. Option C and Option D incorrectly assume that hills must overlap with roads or deserts, which is not guaranteed by the premises. They overextend the given information.


Common Pitfalls:
Many students mentally chain "some" statements as if they forced all overlaps to coincide, leading them to think that the hill rivers must also be the river deserts. This is not necessarily true. Always allow the possibility that different "some" overlaps refer to different elements or regions. Only when an overlap is forced in every possible diagram can you accept a conclusion as logically valid.


Final Answer:
The only conclusion that must follow is that some roads are rivers, so only Conclusion 1 is valid.

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