Sufficient & Necessary Questions - - Question 7

If the city council maintains spending at the same level as this year's, it can be expected to levy a sales tax of 2 ...

JennaArthur October 17, 2019

Will this diagramming eventually become something we can do in our head with less writing?

Questions like these take up a lot of time and diagramming requires quite a bit of writing which will be difficult since the lsat is now paperless. I was wondering if as time goes on and with more practice these questions can almost be done mentally with minimal writing? I imagine after a while wrong choices become obvious. I was just wondering because timing is my greatest concern with the lsat!

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Irina October 17, 2019

@Kaitlyn,

Definitely. Writing it out in the explanations is done only for practice purposes, on a real test you would likely be able to do most of the inferences in your head and only use diagrams for formal logic questions that are harder to visualize otherwise. It is perfectly normal for these questions to take time when you are just starting to study.

For example, for this question as I read it I would mentally make a note that the pattern of reasoning here is IF A THEN B, IF ~B THEN ~A. As you go through the answer choices, you immediately notice that all of them except for the right one introduce a third variable. IF A THEN B, IF ~B THEN C or a variation thereof. (C) is the only one that uses the same two variables for both premises.

Using abstract variables (A, B, C) or (P,Q,R) rather than content-specific variables (e.g, MC for maintain spending) is also generally easier when diagramming as we are only interested in the logical structure rather than the substance of the argument.

Good luck with your studies.

JennaArthur October 17, 2019

Sounds great. Thanks so much!

Ryan-Whyte June 1, 2020

@irina,

This is very helpful. I had the same question as well. Which questions (formal logic) do you suggest we we always diagram rather than infer?