Events & Promotions
|
|
GMAT Club Daily Prep
Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.
Customized
for You
Track
Your Progress
Practice
Pays
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
Jun 0808:00 PM EDT
-10:00 PM EDT
Master the GMAT with expert live instruction, a personalized study plan, and real-time support. Includes 40 hours of online classes plus 6 months of access to the TTP GMAT OnDemand video course. Mon/Wed June 8, 2026 →August 12, 2026 8:00pm-10:00pm EST
Jun 1006:00 AM PDT
-06:15 PM PDT
Register for the GMAT Club Virtual MBA Spotlight Fair – the world’s premier event for serious MBA candidates. This is your chance to hear directly from Admissions Directors at nearly every Top 30 MBA program..- Jun 10
10:00 AM PDT
-11:00 AM PDT
Scoring 715 on the GMAT Focus Edition requires more than just learning formulas, memorizing concepts, or solving hundreds of questions. In this episode, Nishant shares how he improved his GMAT preparation by focusing on application of concepts, and more. 
Jun 1111:00 AM EDT
-01:00 PM EDT
TTP GMAT OnDemand gives serious students 400+ hours of expert video instruction, the full TTP course, AI support, weekly office hours, and a 715+ score guarantee—all built for elite GMAT score improvement.
lavanya.18
Joined: 21 Apr 2024
Last visit: 12 Mar 2025
Posts: 120
Own Kudos:
Given Kudos: 678
Location: India
Concentration: Marketing, General Management
Schools: ESSEC MiM "27 HEC MiM "27 IE LBS MiM "26 INSEAD MiM "26
GPA: 7.5
Products:
30 Sep 2024, 10:48
Kudos
Bookmarks
KarishmaB
Wow! What an amazing question. And great way to explain it. I had fun solving this one!
23 Apr 2025, 22:19
Kudos
Bookmarks
Refutation of the “Must Be True” Assumption in the Set Inclusion Problem
Problem Statement:
A set of numbers has the property that for any number t in the set, t + 2 is also in the set.
If –1 is in the set, which of the following must also be in the set?
Official Answer:
II and III only (i.e., 1 and 5 must be in the set)
Critical Refutation:
The conclusion that 5 must be in the set is logically flawed under strict formal reasoning. Here’s why:
The range of the set is undefined.
The problem does not specify whether the set is finite or infinite.
Therefore, a minimal set such as {–1, 1} satisfies the given property (–1 in the set → 1 in the set) without requiring any further elements such as 3 or 5.
There is no justification for assuming the set contains all numbers generated by repeated additions of 2.
No explicit permission for recursive application.
The property applies to any t in the set and ensures that t + 2 is in the set.
However, the problem never states that this rule can be applied again to the resulting number.
Assuming that t + 2 becomes a new t to repeat the rule requires an implicit assumption that is not supported by the prompt.
“Must be true” requires logical necessity.
According to GMAT standards, an answer must logically follow from the premises without introducing new assumptions.
Since the inclusion of 5 requires interpreting the set as infinite and the rule as recursively applicable, it is not a logically necessary consequence.
Therefore, 5 is not guaranteed to be in the set—it is possible, but not certain.
The prompt gives a condition, not a constructive definition.
The wording describes a property of the set, not a rule for generating its elements from a starting point.
Treating the property as a generator is a logical leap beyond what is explicitly stated.
Conclusion:
Unless we are allowed to assume additional structure (e.g., infinite recursion, constructive rules), none of the answer choices can be said to “must” be in the set based solely on the given information.
Therefore, the correct answer under strict logical interpretation is: cannot be determined.
This exposes a subtle but important conflict between formal logic and the assumed conventions in GMAT-style reasoning.
Problem Statement:
A set of numbers has the property that for any number t in the set, t + 2 is also in the set.
If –1 is in the set, which of the following must also be in the set?
Official Answer:
II and III only (i.e., 1 and 5 must be in the set)
Critical Refutation:
The conclusion that 5 must be in the set is logically flawed under strict formal reasoning. Here’s why:
The range of the set is undefined.
The problem does not specify whether the set is finite or infinite.
Therefore, a minimal set such as {–1, 1} satisfies the given property (–1 in the set → 1 in the set) without requiring any further elements such as 3 or 5.
There is no justification for assuming the set contains all numbers generated by repeated additions of 2.
No explicit permission for recursive application.
The property applies to any t in the set and ensures that t + 2 is in the set.
However, the problem never states that this rule can be applied again to the resulting number.
Assuming that t + 2 becomes a new t to repeat the rule requires an implicit assumption that is not supported by the prompt.
“Must be true” requires logical necessity.
According to GMAT standards, an answer must logically follow from the premises without introducing new assumptions.
Since the inclusion of 5 requires interpreting the set as infinite and the rule as recursively applicable, it is not a logically necessary consequence.
Therefore, 5 is not guaranteed to be in the set—it is possible, but not certain.
The prompt gives a condition, not a constructive definition.
The wording describes a property of the set, not a rule for generating its elements from a starting point.
Treating the property as a generator is a logical leap beyond what is explicitly stated.
Conclusion:
Unless we are allowed to assume additional structure (e.g., infinite recursion, constructive rules), none of the answer choices can be said to “must” be in the set based solely on the given information.
Therefore, the correct answer under strict logical interpretation is: cannot be determined.
This exposes a subtle but important conflict between formal logic and the assumed conventions in GMAT-style reasoning.
30 May 2026, 14:57
Kudos
Bookmarks
Here's my video solution:
Bunuel
