NEW HERE? LEARN MORE
closeclose
Last visit was: 24 Apr 2024, 23:48 It is currently 24 Apr 2024, 23:48
Decision Tracker
My Rewards
New posts
New comers' posts

Close
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

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
Go to My Error Log Learn more
Close
Request Expert Reply
Confirm Cancel

M17-25

SORT BY:
Date
Kudos
   1   2 
Tags:
Find Similar Topics 
Show Tags
Hide Tags
User avatar
B
SrinivasPrabhu
Intern
Intern
Joined: 22 Nov 2022
Posts: 3
Own Kudos [?]: 1 [0]
Given Kudos: 4
Schools: Ross '26 (D)
GMAT 1: 750 Q50 V41
GPA: 3.91
Send PM
Reviews Badge
Re: M17-25 [#permalink] New post   01 Jul 2023, 02:28
Hi Bunuel,

Why cannot option 1 be true for this scenario? What about the case where the set is {1, 1/2, 1/3, .....1/98, 1/99, 1/100}
Isn't i * ai always 1? Which makes 2 * a100 = 2 and a99 + a98 = 2 as well?
User avatar
L
Bunuel
Math Expert
Joined: 02 Sep 2009
Posts: 92901
Own Kudos [?]: 618865 [0]
Given Kudos: 81588
Send PM
CAT Tests Forum Quiz Mode
Re: M17-25 [#permalink] New post   01 Jul 2023, 03:00
Expert Reply
SrinivasPrabhu wrote:
Hi Bunuel,

Why cannot option 1 be true for this scenario? What about the case where the set is {1, 1/2, 1/3, .....1/98, 1/99, 1/100}
Isn't i * ai always 1? Which makes 2 * a100 = 2 and a99 + a98 = 2 as well?


Your scenario will occur when \(a_1=1\). In this case, the sequence will indeed be {1, 1/2, 1/3, ..., 1/98, 1/99, 1/100}. Note that for any term in the sequence, the product of that term and its index (its position number in the sequence) is always 1: \(1*a_1=2*a_2=3*a_3=...=100*a_{100}=1\). However, \(2*a_{100}=a_{99}+a_{98}\) does not hold as \(2*a_{100}=\frac{1}{50}\), whereas \(a_{99}+a_{98}=\frac{1}{98}+\frac{1}{99}=\frac{197}{9702}\neq 2\).

Furthermore, observe that \(i*a_1\) is not always 1. For example, when \(a_1=2\), the sequence becomes {2, 2/2, 2/3, 2/4, 2/5, 2/6, ...} and in this scenario, \(i*a_1=2\), not 1.

Hope it helps.
User avatar
B
JAIDEEP27
Intern
Intern
Joined: 21 Apr 2021
Posts: 3
Own Kudos [?]: 0 [0]
Given Kudos: 498
Send PM
Re: M17-25 [#permalink] New post   23 Jul 2023, 17:48
Hey

So in 'could be true' questions, the statement may or may not be true?

Jai
User avatar
L
Bunuel
Math Expert
Joined: 02 Sep 2009
Posts: 92901
Own Kudos [?]: 618865 [0]
Given Kudos: 81588
Send PM
CAT Tests Forum Quiz Mode
Re: M17-25 [#permalink] New post   24 Jul 2023, 00:54
Expert Reply
JAIDEEP27 wrote:
Hey

So in 'could be true' questions, the statement may or may not be true?

Jai


"MUST BE TRUE" ("ALWAYS TRUE"/"IS TRUE") questions:
    These questions ask which statement is always true for every valid set of numbers. If you can find just one valid set of numbers where a statement is not true, it means the statement is not always true and therefore not the correct answer.

    So, for 'MUST BE TRUE' questions, the plug-in method is good for eliminating an option, but it does not provide a 100% guarantee that an option is always true.

    For "MUST BE TRUE" questions, when using the plug-in method, if you find that more than one option appears to be correct for a particular number or set of numbers, try using different numbers to double-check. Reevaluate only those options that were previously considered correct.

"COULD BE TRUE" questions:
    The questions that ask which of the following statements could be true are different. If you can demonstrate that a statement is true for a specific set of numbers, it implies that the statement could be true and therefore is a correct answer.

You can practice more questions of this type HERE.

Hope it helps.
User avatar
P
BottomJee
DI Forum Moderator
Joined: 05 May 2019
Status:GMAT Club Team member
Affiliations: GMAT Club
Posts: 1031
Own Kudos [?]: 638 [0]
Given Kudos: 1003
Location: India
GMAT Focus 1:
645 Q82 V81 DI82
GMAT 1: 430 Q31 V19
GMAT 2: 570 Q44 V25
GMAT 3: 660 Q48 V33
GPA: 3.26
WE:Engineering (Manufacturing)
Send PM
Reviews Badge CAT Tests Forum Quiz Mode
Re: M17-25 [#permalink] New post   12 Aug 2023, 10:53
I think this is a high-quality question and I agree with explanation.
GMAT Club Bot
gmatclubot
Re: M17-25 [#permalink]
12 Aug 2023, 10:53
   1   2 
Moderator:
Bunuel
Math Expert
92900 posts

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne
Main navigation
GMAT Resources
Partners
MBA Resources
www.gmac.com|www.mba.com | | GMAT Club Rules | Terms and Conditions