LSAT 149 | Section 1 | Logical Reasoning: Q18

LR Question 18 Explanation

QUESTION TEXT: If the standards committee has a quorum, then the…

QUESTION TYPE: Must be True

FACTS:

1. Standards committee quorum ➞ general assembly starts at 6 pm AND not at 7 pm
2. Awards committee quorum ➞ general assembly starts at 7 pm AND not 6 pm

Note: the general assembly can’t start at both 6 and 7 pm, so these two statements can’t both happen.

ANALYSIS: It seems only one committee can have a quorum. We can combine both statements like this:

• Standards quorum ➞ 6 AND not 7 ➞ no awards quorum
• Awards quorum ➞ 7 AND not 6 ➞ no standards quorum

If standards are met and we have a meeting at 6 and not 7, then we violate the necessary condition for an awards quorum (meeting at 7). So, we can conclude “no awards quorum”. The same applies if there is an awards quorum: we can say there is no standards quorum.

Note that we don’t know what happens if there is no quorum. And starting at 6 or 7 doesn’t prove that anyone has a quorum. It only proves who doesn’t have a quorum. It’s possible nobody has a quorum!

___________

1. Look at the diagram above: not 6 ➞ no standard quorum. That’s all we can prove.
2. Look at the diagram above. “No standards quorum” is a necessary condition. Necessary conditions don’t lead anywhere. We can only move left to right on the diagram.
3. This is an incorrect reversal of the first sentence. It’s possible there are other reasons for having a meeting at 6 pm. Maybe nobody has a quorum, but the chairperson decided to start early so they could get home in time for bed.
4. Same as C. It’s possible nobody has a quorum! The meeting not begin at 7 for other reasons. All we can say is “not 7 ➞ no awards quorum”. Lots of things can cancel a meeting: maybe the building caught fire.
5. CORRECT. This follows the logic above. If standards has a quorum, the meeting starts at 7. This means it doesn’t start at 6. If we take the contrapositive of the second statement, we get this: “Not at 6 ➞ no awards quorum”. So, it isn’t possible for both committees to have a quorum at the same time.

Recap: The question begins with “If the standards committee has a quorum, then the”. It is a Must be True question. Learn more about LSAT MBT questions in our guide to LSAT Logical Reasoning question types.