Lesson: Introduction to Critical Reasoning

Comment on Introduction to Critical Reasoning

hey dont we have any source of question for practicing?
gmat-admin's picture

For each question type (Assumption questions, Paradox questions, etc), there are several related practice questions in the box beneath the video. For example, you can see the practice questions related to Weaken the Argument questions: https://www.gmatprepnow.com/module/gmat-critical-reasoning/video/1136

Also, on the Critical Reasoning page (https://www.gmatprepnow.com/module/gmat-critical-reasoning), you will find several video practice questions AND even more links to practice questions (at the bottom of that page).

So the only difference between an assumption and a premise is that the assumption is NOT stated whereas premises are? Am I thinking about this correctly?
gmat-admin's picture

That's correct.

Hi Brent,

Does it mean that, if we take the assumption like the one you mentioned "Gary's history of lateness will be repeated today" and put it in the sentence next to premises:

For the past 3 days, Gary has arrived late for work. This morning, while Gary was driving to work, his car got a flat tire. In addition, Gary's history of lateness will be repeated today. Therefore, Gary will be late for work today.

It becomes a premise itself,

By that, I must understand the assumption is a hidden statement that is implied together with stated premises when making the final conclusion.

Am I correct,
gmat-admin's picture

Yes, if we state an assumption, it becomes a premise.



This one is about reducing the risk of polyps and the answer is about the time after polyps have developed already. How does that work?
gmat-admin's picture

Question link: https://www.beatthegmat.com/calcium-t279620.html

The original argument suggests that low calcium levels CAUSE polyps. If that were true, then eating food rich in calcium would help prevent polyps.

However, we're not told that low calcium levels cause polyps; we're told that the two things seem to be related, but there's no clear cause and effect.

So, what if it's the other way around? What if polyps CAUSE low calcium levels? If that were the case, then eating food rich in calcium would NOT help prevent polyps.

Answer choice C indirectly tells us that polyps CAUSE low calcium levels.

So C is the best answer.

Does that help?

Hi Brent, could you please help me with this question please? Thanks!!

Which of the following most logically completes the passage?

Using new detection techniques, researchers have found trace amounts of various medicinal substances in lakes and rivers. Taken in large quantities, these substances could have serious health effects, but they are present in quantities far too low to cause any physiological response in people who drink the water or bathe in it. Nevertheless, medical experts contend that eliminating these trace amounts from the water will have public health benefits, since __________.
A. some of the medicinal substances found in lakes and rivers are harmless to humans even if taken in large quantities
B. some of the medicinal substances found in lakes and rivers can counteract possible harmful effects of other such substances found there
C. people who develop undesirable side effects when being treated with medicines that contain these substances generally have their treatment changed
D. most medicinal substances that reach lakes or rivers rapidly break down into harmless substances
E. disease-causing bacteria exposed to low concentrations of certain medicinal substances can become resistant to them
gmat-admin's picture

I would classify this as a Paradox question.

We're told that low levels of medicinal substances are essentially harmless.
Yet, the experts say that removing these harmless substances we'll have public health benefits.

This seems paradoxical. If the substances are HARMLESS, how can removing them be a public health benefit?

E. disease-causing bacteria exposed to low concentrations of certain medicinal substances can become resistant to them
This answer tells us that low concentrations of medicinal substances can make disease-causing bacteria stronger (which would be a threat to public health).
In other words, the low levels of medicinal substances INDIRECTLY cause a threat to public health.
As such, removing those medicinal substances would improve public health benefits.

Hi Brent, could you help me with this question please? Thank you x

United Lumber will use trees from its forests for two products. The tree trunks will be used for lumber and the branches converted into wood chips to make fiberboard. The cost of this conversion would be the same whether done at the logging site, where the trees are debranched, or at United's factory. However, wood chips occupy less than half the volume of the branches from which they are made.

The information given, if accurate, most strongly supports which of the following?

(A) Converting the branches into wood chips at the logging site would require transporting a fully assembled wood-chipping machine to and from the site.

(B) It would be more economical to debranch the trees at the factory where the fiberboard is manufactured.

(C) The debranching of trees and the conversion of the branches into chips are the only stages in the processing of branches that it would be in United's economic advantage to perform at the logging site.

(D) Transportation costs from the logging site to the factory that are determined by volume of cargo would be lower if the conversion into chips is done at the logging site rather than at the factory.

(E) In the wood-processing industry, branches are used only for the production of wood chips for fiberboard.
gmat-admin's picture

This is a Conclusion question so, as we examine each answer choice, we must ask ourselves "MUST this be true?"

(A) There's nothing in the passage that suggests the wood-chipping machine MUST be fully assembled during transportation. For example, the wood-chipping machine could be assembled at the logging site. ELIMINATE.

(B) There's nothing to suggest this. If anything, the passage suggests that it would be more economical to debranch the trees at the logging site. ELIMINATE.

(C) The passage mentions only two types of processing. However, it is conceivable that there are additional, unmentioned, processes that may be more economical to perform at the logging site. ELIMINATE

(D) Since wood chips occupy less than half the volume of the branches from which they are made, then transportation costs would, indeed, be lower if those costs were determined by volume. KEEP

(E) there is nothing in the passage that suggests that this MUST be true.

Answer: D


'Gary's house is 1 block away from work.' Are we allowed to use 'common sense' on the GMAT questions to strengthen or weaken an argument? I'm thinking if this statement was 'Gary's house is 3 miles from work' - I'm not sure if this would strengthen or weaken the argument as it is very relative in nature.
gmat-admin's picture

Great question!

Yes, you'll definitely need to apply some common sense with Critical Reasoning questions. Having said that, you won't be required to know specific facts such as:
- species of snakes that are poisonous
- capital cities of the world
- number of feet in a mile

Even in the case of Gary's flat tire, the GMAT would likely add some additional information that would help us see that living only a block away from work would weaken the conclusion. For example, there might also be information that notes Gary doesn't suffer from any mobility issues.


Hello sir
Should i complete all videos then go for practice or go with topicwise video then og?
gmat-admin's picture

I suggest that, upon watching a video on a certain topic (e.g., Assumption questions), you answer at least three or four questions to practice/reinforce the concepts and strategies covered in that lesson.

Later on, during stage 2 of your prep, you'll have the opportunity to revisit any topics that you're still struggling with.

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