David Always Tells the Truth on Mondays... Forum

[Mjvance2]

I don't know how many of you have seen the following logic problem, but I wanted to see if anyone came up with the same answer that I did. I wanted to give it a good LSAT treatment, so I thought it would be good to post it here. Hopefully it gives everyone a good chance to evaluate their logical reasoning skills.

"David always tells the truth on Mondays, Thursdays, and Saturdays, but lies on every other day.

If David says, "I will tell the truth tomorrow," then what day is it?

Wednesday

Tuesday

Friday

Sunday

[somethingElse]

I love riddles!

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Tuesday, right? Because since M TH and SA are True days and TU W F and SU are false days, the only day he could say "Tomorrow I will tell the truth" and have it "line up" with the next day is TU. He would be saying "tomorrow I will tell the truth" on a false day, and the next day is a false day as well making the two "line up." Tuesday (and Wednesday) is the only way this lining up can happen.

[RZ5646]

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It can't be a truth day, and it can't be a lying day right before a truth day. That just leaves Tuesday.

[ihenry]

It has to be a non-final day in consecutive truth days or lie days, because neither truth-lie nor lie-truth would work, which only leaves

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Tuesday.

[jetsfan1]

Gonna pop in here and nitpick...

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I got Tuesday too, but technically the prompt only tells us that David ALWAYS tells the truth Mon, Thurs, and Fri. However, with Tues, Wed, Fri, and Sun we only know that he lies at least one time. We do not know that he ALWAYS lies on those days. If this is the case, he could tell the truth about telling the truth tomorrow on those days as well (and lie about something else that day, like if he ate his veggies). So the correct answer could be any of the 4. I realize that's not the intent, and its supposed to be read to get Tuesday, but since this is an LSAT prep thread...

Definitely could be read that way, no?

[Mjvance2]

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I got Tuesday too, but technically the prompt only tells us that David ALWAYS tells the truth Mon, Thurs, and Fri. However, with Tues, Wed, Fri, and Sun we only know that he lies at least one time. We do not know that he ALWAYS lies on those days. If this is the case, he could tell the truth about telling the truth tomorrow on those days as well (and lie about something else that day, like if he ate his veggies). So the correct answer could be any of the 4. I realize that's not the intent, and its supposed to be read to get Tuesday, but since this is an LSAT prep thread...

YES!!! That's the answer I was looking for. Exactly the same thing I thought.

[jetsfan1]

[+] Spoiler

I got Tuesday too, but technically the prompt only tells us that David ALWAYS tells the truth Mon, Thurs, and Fri. However, with Tues, Wed, Fri, and Sun we only know that he lies at least one time. We do not know that he ALWAYS lies on those days. If this is the case, he could tell the truth about telling the truth tomorrow on those days as well (and lie about something else that day, like if he ate his veggies). So the correct answer could be any of the 4. I realize that's not the intent, and its supposed to be read to get Tuesday, but since this is an LSAT prep thread...

YES!!! That's the answer I was looking for. Exactly the same thing I thought.