Free LSAT Practice
LSAT Practice Test
LSAT Practice Test Videos
eBook: The Road to 180
Law School Top 100
LSAT Test Proctor
LSAT Logic Games
Apple App Store
Digital LSAT Simulator
Campus Rep Internship
Fee Waiver Scholarship
LSAT Test Dates
LSAT Message Board
October 2005 LSAT
If switch 1 and switch 3 are both off, then which one of the following could be two switches that are both on?
on July 10 at 04:39PM
Why is A the correct answer?
on July 10 at 06:07PM
Happy to help. Let's take a look at (A).
Here are the main rules in this game:
1) 1 - >/3
1 - >/5
2) 4 - >/2
4 - >/5
3) circuit load corresponds to one of the switch numbers that's on
We're told that 1 and 3 are both off, and we're looking to figure out
which answer choice could be two switches that are both on.
Starting with (A), we have 2 and 7. Let's try it.
If 2 and 7 are both on, this means that 4 must be off (the
contrapositive of rule 2).
We have 2 and 7 on, and 1, 3, and 4 off with 5 and 6 not yet assigned.
Looking at our rules, we see that with 2 and 7, we already satisfy the
last rule (the switch whose number corresponds to the circuit load of
the panel is itself on). We can just put 5 and 6 in the out/off group,
so we have 2 and 7 in and all of the other switches out. This is why
(A) works and is the correct answer choice.
Does this make sense? Let us know if you have any other questions!
Posting to the forum is only allowed for members with active accounts.