LSAT 149 | Section 1 | Logical Reasoning: Q21

LR Question 21 Explanation

QUESTION TEXT: Archaeologist: Our team discovered 5,000 year old…

QUESTION TYPE: Necessary Assumption

CONCLUSION: Canada’s aboriginal people probably build birchbark canoes 5,000 years ago.

REASONING: Archaeologists found copper tools near birch, cedar and spruce trees. These trees are used to make canoes, and these tools are currently used to make canoes.

ANALYSIS: This sounds like a super persuasive argument. I couldn’t really prephrase anything. If no prephrase comes to mind, it’s best to just go to the answers, narrow it down to 1-3 most plausible ones, and negate them.

___________

1. Trade value isn’t relevant. The author wasn’t even assuming there was more than one tribe in the area the tools were found. Their argument was only about the use of the tools.
2. CORRECT. The author only said the tools were found in a good location, and that the tools are 5,000 years old. But we don’t know if the tools were always in that spot. Maybe the tools were moved there more recently. If the tools weren’t present in the region 5,000 years ago, then they can’t be evidence about canoe-building 5,000 years ago. You can’t build a canoe if the tools don’t exist in your area!
   Negation: The tools were not in the region 5,000 years ago.
3. This doesn’t matter. It only matters that the tools would work on the three trees in question. If they work on wood from even more trees, great!
4. It doesn’t matter if they were the only tools. It only matters that they were canoe making tools, and that they were enough to make canoes on their own.
    
   E.g. If you’re using a phone to write a note, it doesn’t matter that a computer is also a tool used for writing notes. The phone is independently sufficient.
   Negation: There were other tools used for making canoes in another region. However, the tools found in this region are sufficient to make canoes.
5. This is a trap answer. You might have picked this thinking “maybe these tools are so general that they don’t indicate canoe-making”. That’s a good thought, but for that, this answer should have said “The tools were not general tools that have many used beyond canoe-making”.
    
   This answer leaves open the possibility of there being 1-2 marginal alternative uses, which doesn’t detract from the tools being largely for canoes.
    
   For a modern example, you probably use a screwdriver mostly for screwing in screws, but perhaps you sometimes use it to open beer bottles. This doesn’t negate the screwdriver’s primary use!
   Negation: The tools are known for mainly being canoe tools, but are also used for 1-2 small tasks.

Recap: The question begins with “Archaeologist: Our team discovered 5,000 year old”. It is a Necessary Assumption question. Learn how to master LSAT Necessary questions on the LSAT Logical Reasoning question types page.