Self-study
If the standards committee has a quorum, then the general assembly will begin at 6:00 P.M. today. ██ ███ ██████ █████████ ███ █ ███████ ████ ███ ███████ ████████ ████ █████ ██ ████ ████ ██████
The General Assembly Can "Begin" Just Once
This stimulus gives us two conditional rules.
Rule 1: If the standards committee has a quorum, then the general assembly will begin at 6:00 P.M. today.
Rule 2: If the awards committee has a quorum, then the general assembly will begin at 7:00 P.M. today.
There's a critical detail hiding in the interaction between these two rules. There's only one time that "the" general assembly can "begin" today. So if the general assembly begins at 6:00 P.M., it does not begin at 7:00 P.M. And if it begins at 7:00 P.M., it does not begin at 6:00 P.M. This lets us connect the two rules into a chain.
Starting from Rule 1: if the standards committee has a quorum, the general assembly begins at 6:00 P.M. If it begins at 6:00 P.M., then it doesn't begin at 7:00 P.M. And by the contrapositive of Rule 2, if the general assembly does not begin at 7:00 P.M., then the awards committee does not have a quorum.
Putting it all together:
standards committee has quorum → GA begins at 6 P.M. → GA does NOT begin at 7 P.M. → awards committee does NOT have quorum
The same logic works starting from Rule 2:
awards committee has quorum → GA begins at 7 P.M. → GA does NOT begin at 6 P.M. → standards committee does NOT have quorum
Want a visual?
Each committee's quorum locks the GA into a specific start time:
standards quorum → GA starts here
awards quorum → GA starts here
5 PM
6 PM
7 PM
8 PM
9 PM
The GA can only start once. If it starts at one time, it can't start at the other.
So if the standards committee has a quorum, the entire chain plays out like this:
standards committee
has quorum
→
has quorum
GA begins
at 6 P.M.
→
at 6 P.M.
GA does NOT
begin at 7 P.M.
→
begin at 7 P.M.
awards committee
does NOT have quorum
does NOT have quorum
Anticipation
Since this is a Must Be True question, we want an answer that is guaranteed by the stimulus. The correct answer will almost certainly be something that we can find on this conditional chain.
18.
Which one of the following ██████████ ███████ █████████ ████ ███ ██████████ ██████
a
If the general ████████ ████ ███ █████ ██ ████ ████ ██████ ████ ███ ██████ █████████ ███ █ ███████
If the general assembly does not begin at 6:00 P.M., the contrapositive of Rule 1 tells us the standards committee does not have a quorum. But that tells us nothing about whether the awards committee has a quorum. The awards committee might have a quorum, or it might not.
b
If the standards █████████ ████ ███ ████ █ ███████ ████ ███ ██████ █████████ ███ █ ███████
Just because the standards committee doesn't have a quorum doesn't mean the awards committee does. Both committees could lack a quorum. The two rules tell us what happens if each committee has a quorum, but neither rule tells us that at least one committee must have a quorum.
c
If the general ████████ ██████ ██ ████ ████ ██████ ████ ███ █████████ █████████ ███ █ ███████
This reverses the logic of Rule 1. Rule 1 says the standards committee having a quorum is sufficient for the general assembly to begin at 6:00 P.M., not necessary for it. "If A then B" does not prove "If B then A."
d
If the general ████████ ████ ███ █████ ██ ████ ████ ██████ ████ ███ █████████ █████████ ███ █ ███████
If the general assembly does not begin at 7:00 P.M., the contrapositive of Rule 2 tells us the awards committee does not have a quorum. But that tells us nothing about whether the standards committee has a quorum.
e
If the standards █████████ ███ █ ███████ ████ ███ ██████ █████████ ████ ███ ████ █ ███████
This follows from the conditional chain. If the standards committee has a quorum, Rule 1 tells us the general assembly begins at 6:00 P.M. Since there's there's only one single time that "the" general assembly can "begin", beginning at 6:00 P.M. means it does not begin at 7:00 P.M. And by the contrapositive of Rule 2, if the general assembly does not begin at 7:00 P.M., the awards committee does not have a quorum. So the standards committee having a quorum guarantees that the awards committee does not have a quorum.