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I'm confused about a few conditional logic question

"Unless the field dries, the game cannot be played." -dries>-game played

"Unless the street is dark, Jeff walks home from work. The street is dark only on the weekends." -Jeff walks home>street dark>weekend

That unless equation is very confusing for me. So I need an explanation for that.. How do I know which one is necessary and which one isn't?

Why would can't it be

game played>field dries

Another question I have is PT15, S3, Q7

It starts with "Unless" and for that question I negated the "nation redistributes" part. And then I negated argument and worked backwards to the correct answer. So why wouldn't this work the same way? I am confused.

Why couldn't I negate -street dark>Jeff Walks home..

I am very confused..

Not sure I understand your question fully but you are allowed to negate it the way you've done it; moreover, ~street dark ---> Jeff Walks Home is valid as it's just the contrapositive of what you have above
(~Jeff walks home ---> street dark ---> weekend).

"Unless the field dries" has the exact same meaning as "If the field does not dry." Hopefully that makes it easier to understand.

Tim0thy222 wrote:"Unless the field dries" has the exact same meaning as "If the field does not dry." Hopefully that makes it easier to understand.

"Unless the street is dark, Jeff walks home from work. The street is dark only on the weekends." -Jeff walks home>street dark>weekend

Kind of like this:

(if) the street is (not/unless negation) dark, Jeff walks home from work. The street is dark ONLY on weekend.

My issue is how do I like that with weekend?

The answer in the Manhattan book chapter 8 on page 345 is "-Jeff walks home>street dark>weekend"

I don't see where do I link weekend if the weekend is the necessary condition for street dark.

Is it like this then? (Unless negates street dark and weekend), If the street is NOT dark, then NOT weekend, Jeff walks home.

b33eazy wrote:

Tim0thy222 wrote:"Unless the field dries" has the exact same meaning as "If the field does not dry." Hopefully that makes it easier to understand.

"Unless the street is dark, Jeff walks home from work. The street is dark only on the weekends." -Jeff walks home>street dark>weekend

Kind of like this:

(if) the street is (not/unless negation) dark, Jeff walks home from work. The street is dark ONLY on weekend.

My issue is how do I like that with weekend?

The answer in the Manhattan book chapter 8 on page 345 is "-Jeff walks home>street dark>weekend"

I don't see where do I link weekend if the weekend is the necessary condition for street dark.

Is it like this then? (Unless negates street dark and weekend), If the street is NOT dark, then NOT weekend, Jeff walks home.

The weekend is a necessary condition for the street being dark.
The street being dark is a necessary condition for the Jeff NOT walking home.

So if Jeff doesn't walk home...that forces the fact that the street IS DARK, which then in turn forces the fact that it is the WEEKEND.

Don't really understand what you don't get.

Edit: I think what you're not seeing is the contrapositive of the "If not dark, then Jeff walks home" statement.

That last statement you made is incorrect for the following reason.

If the street is not dark, then it could still be the weekend.

All this scenario tells us about the weekend is that
1) if it is dark, it is the weekend
2) if it is not the weekend, it is not dark, and therefore Jeff walks home.

Knowing that it is the weekend wouldn't tell us anything, because it may or may not be dark, and Jeff may or may not walk home.

Does this help? I'm having trouble identifying exactly where you're having trouble.

ETA: Scooped. Pretty much the same thing boblawlob said.

I think my problem is just understanding conditional logic. I've been going through the Mahattan and powerscore book. For example, I got completely confused by PT18, S2, Q23. I just did not get it.

b33eazy wrote:I think my problem is just understanding conditional logic. I've been going through the Mahattan and powerscore book. For example, I got completely confused by PT18, S2, Q23. I just did not get it.

Whew, PT18, S2, Q23 was pretty tricky. I just went ahead and did the problem.

Okay, first of all, the wording of that problem is really what makes it difficult.

Let's work through it together:

Stem: Each of the following could be true of teachers who have enabled their students...

SMD= Students make their own decisions
TMD= Teachers have the power to make decisions
IL= Independent Learners
ET= Effective Teachers

Teachers are effective only when they help their students become independent learners.
IL---->ET; contrapositive: ~ET---->~IL

In order for the teachers to enable their students, they must have the power to make their own decisions.
SMD--->TMD; contrapositive: ~TMD---->~SMD

Students' capability to make their own decisions is essential to their becoming independent learners.
IL--->SMD; contrapositive: ~SMD--->~IL

Now, let's go through the answer choices.

A) This can still be possible. Because, while enabling the decision making process of the students is a necessary function, it is not sufficient. So, the students CAN still be dependent.

B) Once again, this can still be true, because, while it is necessary for teachers to have enabled their students to make decisions, it is not sufficient; the students could still be dependent. Read: ~ET---->~IL (If the students are not independent, then the teacher is not effective).

C) Once again, this choice is possible, because the students COULD become independent, thus accomplishing the sufficient requirement for teachers to become effective.

D) This is necessary for the teachers to accomplish in order for them to enable the students to make decisions, so this answer is definitely possible.

E) This is the correct answer. Since the stem assumes that the teacher is enabling the decision making process of the students, they have to already be able to make decisions in their classroom. SMD--->TMD; contrapositive: ~TMD---->~SMD. This breakdown indicates that it isn't possible, given the situation, for the teacher to not be able to make decisions in their own classroom.

When I answer these types of questions, I don't usually write any of these things down-- it would take too long. Instead, I try to connect points in my head.. and if there is a violation, then I can home in on the problem.

I hope that this helps!

It does help thank you! It's a process and I just have to keep working on the LR!