If the average (arithmetic mean) of 6 numbers is 75, how

Yes, if we were told that exactly 4 out of 6 numbers equal to 75 then statement (1) would be sufficient.

Hi All,

This question is remarkably similar to a question found in the last few Official Guides:

In the OG13 and GMAT2015: page 288 #146
In the GMAT2016: page 292 #157

GMAT assassins aren't born, they're made,
Rich

The question is really good, but the statement 1 creates confusion as to if 4 numbers are equal to 75 or exactly 4 numbers are equal to 75.... I don't think any such ambiguous question is asked in the exam as GMAT is renowned for clean questions. They are required to test QA skill and not ambiguity skill here. Many people have done mistake in this question just because of the language of statement 1 which justifies the ambiguity of the statement 1. If someone can give reference to similar question from OG it would be highly helpful (Do provide the GMAT Club link of the same). Bunuel can you throw some light in this regard.

Anyway we can write the solution as per the original answer as below :

AM of 6 numbers 75.
DS : How many numbers are greater than 75.

Statement 1 : 4 numbers are equal to 75.
We don't know about the other 2 numbers
2 possibilities : (a) one number is smaller than 75 and the other number is greater than 75 (b) Both numbers are equal to 75.
NOT SUFFICIENT

Statement 2 : One number is less than 75
We don't know about the other 5 numbers.
NOT SUFFICIENT

Combined :
one number is smaller than 75 and the other number is greater than 75
SUFFICIENT


Answer C

Hi - why is S2 not sufficient ...

is it because it doesnt confirm if "only" one number is below 75 ?

is that the reason...

Yes but we also don't know know how many numbers are equal to 75.

This question is brilliant at testing DS.
It just took me around 4 minutes to solve this question.

I got confused with statement 2 -- if it means -- exactly one number is less than 75 or that one of the six numbers is less than 75.

Hi bunuel

Have you seen any gmatprep or OG questions actually testing this concept ?

this doesn't seem like a logic or reasoning question but more of a discrepancy like question

Could you perhaps give an example of a gmat prep or OG question testing something like this

Posted from my mobile device

Hi jabhatta@umail.iu.edu,

This question is remarkably similar to a question found in the last few Official Guides (going all the way back to the OG13). In the two most recent versions, the question can be found here:

GMAT2019 pg. 286 DS #396
GMAT2020 pg. 293 DS #452

GMAT assassins aren't born, they're made,
Rich