"there are no professors under the age of eighteen."
So: if there is a professor, then she is not under the age of eighteen
P1: P ==> not U18 U18 ==> not P
"no one under eighteen can vote legally."
So: if you are under the age of eighteen, then you cannot vote legally.
P2: U18 ==> not VL VL ==> not U18
"some brilliant people are professors."
Q1: BP-some-P P-some-BP
"some are legal voters," (NOTE: we will diagram "legal voters" as "VL" to keep the variables as consistent as possible.)
Q2: BP-some-VL VL-some-BP
"some are under eighteen."
Q3: BP-some-U18 U18-some-BP
We can conclude answer choice (E): "Some brilliant people are neither professors nor legal voters."
We can conclude this by combining "Q3" with the contrapositive for "P1" like so: BP-some-U18 ==> not P to infer: BP-some-not P, i.e. some brilliant people are not professors, and by combining "Q3" with "P2," like so: BP-some-U18 ==> not VL to infer: BP-some-not VL, i.e. some brilliant people are not legal voters. So, as you can see, there are some brilliant people that are not professors and are not legal voters.
Hope that helps clear things up! Please let us know if you have any other questions.
yababio May 21, 2015
Video please
NazMay 21, 2015
There is no need for a video explanation to this question since it has no major visual components. Please refer to the written explanation above for a breakdown of the problem.
Hope that helps! Please let us know if you have any other questions.
jmn5617October 16, 2015
I understand why E is correct however could someone please explain why C does not necessarily have to be true?
NazOctober 17, 2015
As explained in the thread above, we can diagram the statements like so:
P1: P ==> not U18 U18 ==> not P
P2: U18 ==> not VL VL ==> not U18
Q1: BP-some-P P-some-BP
Q2: BP-some-VL VL-some-BP
Q3: BP-some-U18 U18-some-BP
Remember we are looking for what MUST be true, not what COULD BE true.
Answer choice (C) states: Some legal voters are not professors.
(C): VL-some-not P not P-some-VL
We have no information that would lead us to concluding answer choice (C) definitively. We merely know that some brilliant people are professors and that some brilliant people are legal voters. This means that some legal voters might not be professors, but they also might be. Therefore, we cannot say answer choice (C) MUST BE TRUE.
Hope that helps! Please let us know if you have any other questions.
irinacioncaNovember 9, 2017
Why is A not correct?
A video would really be helpful for this one as it is very long to diagram. Thanks
KimJongUnAugust 21, 2018
Are there any fast tricks or helpful hints that Naz used? I diagramed Q1-3 and Q1&2 both lead to notU18. As a timesaver, how could I avoid this. And be as efficient as Naz?
KimJongUnAugust 21, 2018
Are there any fast tricks or helpful hints that Naz used? I diagramed Q1-3 and Q1&2 both lead to notU18. As a timesaver, how could I avoid this. And be as efficient as Naz?
MehranAugust 21, 2018
Hi @KimJongUn, thanks for your post. Diagramming gets easier and more efficient the more you do it. There are no "fast tricks." Spending time diagramming sufficient and necessary reasoning during untimed LSAT practice can help you efficiently and accurate diagram where helpful during timed practice. Keep at it!
