LR Question 20 Explanation, by LSATHacks
QUESTION TEXT: Council member: The profits of downtown businesses…
QUESTION TYPE: Must Be True
FACTS:
- More consumers downtown means more profits for downtown businesses.
- A decreased cost of living downtown means that more consumers will live there.
- The profits of downtown business will not increase unless congestion decreases.
ANALYSIS: This is counterintuitive. We’re told profits can’t increase unless congestion decreases. But that just means less congestion is a necessary condition for increased profits. We can reword statement three as:
“If profits increase then congestion will decrease.” It’s odd, but logically true based on the stimulus.
We can combine all three statements.
Decreased cost of living ➞ More consumers ➞ More profits ➞ less congestion
Logically, that does work. Lower cost of living and more people lead to less congestion. More consumers lead to more profits, always. And if profits go up then congestion goes down…somehow.
So answer choice B is correct even though it doesn’t mention congestion.
___________
- We don’t know. We only know that downtown traffic can prevent an increase in profits.
- CORRECT. The first two sentences tell us this. Lower cost of living equals more consumers. More consumers lead to more profits. It’s the first three statements in the logical chain above.
- Same as A. We only know that traffic is somehow related to profits. We don’t know if it is related to cost of living.
- Same as A and C. We have no idea if or how traffic congestion is related to cost of living.
- This mixes things up. The number of consumers present increases profits. But increased profits might not draw in more consumers.
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I needed to write this out to get the correct answer using a shorthand/formal logic approach to save time instead of writing out full sentences. But it still takes too long. How can you arrive at the correct answer more quickly on test day?
Yeah in practice you’d do 1-2 letter diagrams. This one was just tricky because it had multiple C’s, but you could draw like this:
CL↓ ➞ Cons↑ ➞ P↑ ➞ Cong↓
Apart from that, keep a list of any questions with diagrams and redo them like logic games to get faster. You can also check out this article about going faster on LR: https://lsathacks.com/guide/faq/how-to-go-faster-logical-reasoning/
Finally, the courses in LSATHacks Pro have a LOT of speed tips, especially the LR mastery seminar, so if you still need more help I’d check that out: https://lsathacks.com/lsathacks-pro/
I am confused on this one. I thought the last sentence meant the profits will not increase if the traffic doesnt decrease. I didnt understand how it could mean that if more people live there traffic congestion will decrease. Please help.
Unless can be a tricky one do understand. You negate the thing before unless and make it sufficient. Then the thing after unless is necessary. So:
Profits not increase unless traffic decrease = profits increase –> Traffic decrease.
What you stated was the incorrect negation of the sentence. As for more people living there = decrease, that comes from chaining all the statements together. Practicing conditional logic can help with questions like this. For members of LSATHacks, I have a practice tool here: https://lsathacks.com/lsat-logic-tool/
Note: This is an old comment but I wanted to clarify the point.
If decreasing traffic congestion is a necessary condition for profits to increase, then how can we know that profits will increase without any information about traffic?
We know that if the cost of living decreases, then profits increase, and we also know from the last sentence of the stimulus that if profits increase, then traffic congestion necessarily decreases. So, although the answer choice does not explicitly give us any information about traffic, we know something about the effect of the answer choice on traffic based on the information in the stimulus.