Q10 - If a person chooses to walk

[nfagin]

I can eliminate A, D, and E as being incorrect. And although C doesn't necessarily strengthen the argument, I can't figure out how B strengthens it. Am I missing something between the lines? I'm just not understanding how non-moving cars and congestion have anything to do with making the argument stronger.

[nfagin]

Is B somehow supposed to refute a claim that car-pooling will greatly reduce pollution, by showing that in cases of congestion this is less likely? That's all I could come up with.

[ManhattanPrepLSAT1]

This argument says that if a person chooses to walk, rather than drive, there is one less vehicle emitting pollution. Therefore, if people walk whenever possible, then pollution will be greatly reduced.

This argument assumes that there are instances that people could walk but choose to drive. But the question stem asks us to strengthen the argument, not find the assumption. However, if the assumption were present in the answer choices, providing the assumption would strengthen the argument. But the assumption is not in the answer choices... So, anything that makes the conclusion a little more likely to be true would be the correct answer.

If a lot of the cars that are on the road are stuck in traffic, and non-moving cars still emit pollution, and the greater the number of cars on the road, the greater the chance you're stuck in traffic, then getting any cars off the road will lead to a lower chance of being stuck in traffic and also less pollution. Answer choice (B) says that if you get cars off the road, not only will you reduce pollution by removing a pollution emitting vehicle from the road, you're also lowering the chance that everyone else will be stuck in traffic, thereby reducing the pollution that the other cars emit.

Incorrect Answers
(A) weakens the argument by saying that we won't be able to get more cars off the road. If we can't reduce the number of polluting cars, it will be hard for us to reduce pollution.
(C) is irrelevant. That some cars pollute more than others doesn't help us in reducing pollution because we don't know which cars we will be taking off the road, if we choose to walk rather than drive.
(D) is irrelevant. We're not talking about switching to buses, we're talking about choosing to walk.
(E) weakens the argument. If some who were riding are now going to be driving because their old ride is now choosing to walk, then we haven't reduced the number of vehicles on the road. Pollution wouldn't be decreased by as much as the argument hopes if answer choice (E) were true.

[fch4mat]

I got a little lost reading your explanation for B. However, the way I understand it (beside process of elimination-it was the only answer choice left) is, B states that even though non-moving vehicles emit half of the pollution as moving cars, by having more cars non-moving than moving, you are still emitting pollution and there not necessarily reducing the pollution in the air. This strengthens the argument by supporting the fact that pollution would be greatly reduced if only people would walk, as opposed to being in non-moving running vehicles.

Does that make any sense?

[ManhattanPrepLSAT1]

Yeah, that's it!

If congestion means more nonmoving vehicles and nonmoving vehicles are emitting pollution (even if it's less than moving vehicles) that's going to support the conclusion that getting people to walk rather than drive would reduce pollution.

This question is just like the real world (at least in LA!). The more cars, the more everyone is stuck in traffic and not moving. Even though these cars are not moving, they're still emitting pollution. So, getting people off the road would help get rid of congestion, get the remaining cars moving again, and reduce pollution.

[ldanny24]

My problem with answer (b) is that it includes nonmoving vehicles emitting half as much pollution as moving vehicles. If more people decided to walk then wouldn't that clear up room for more emission producing moving cars? And since we don't really know the amount of cars that would be taken off, any benefit pollution wise received from removing more stationary cars could be offset by moving cars.

These forums are AWESOME!

[ManhattanPrepLSAT1]

Glad you like it here! It's a great community of LSATers...

I see your thought, but I think you might benefit from just thinking about your average freeway in a major city - and what that looks like at 2am vs at 6pm on any given Tuesday. During rush hour no one is moving and the cars are just sitting there emitting pollution. At night the freeway es empty. Cars zip along, and much less pollution is emitted.

Regardless, if people choose to walk when it is feasible for them to, that would mean that we would have fewer drivers. So your line of reasoning takes a wrong turn when you allow for more drivers to replace the non-moving ones.

If more people decided to walk then wouldn't that clear up room for more emission producing moving cars?

That's the wrong turn, because the conclusion would reduce the number of drivers, thereby reducing congestion, and reducing pollution.

What do you think, does that make sense?

[ldanny24]

Yeah, I can see how that sentence you quoted from me might be misinterpreted, but I really wasn't making that leap in logic. I'm not saying that more moving cars would replace nonmoving ones, I'm saying that the lessening of nonmoving cars would allow room for cars to move. And since these moving cars would emit double the pollution of stationary cars, couldn't we say that any benefit gained from drivers refusing to drive be offset by the more pollution producing moving cars?

So for example,

If there are 500 cars on a particular freeway and this is jamming up traffic where hypothetically X amount of pollution is emitted, wouldn't reducing the number of cars to 250 where drivers could freely move thereby doubling pollution still emit X amount?

[ManhattanPrepLSAT1]

Thanks for clarifying. I definitely don't want to misinterpret your statements. And again, I can see where you're coming from but we need to adjust the some of your considerations to get a clearer picture.

Let's make it personal. Suppose you drive to work each day, and that commute would take you 20 minutes if you could drive it at midnight. But during the morning you're fighting with everyone else who wants to share the road with you. Suppose at 9am that same trip takes you 45 minutes because at this one stoplight you have to sit and wait for 25 minutes in a backup.

Which trip will emit more pollution? I would suspect that the one that took you 45 minutes would emit more pollution since your car is running longer and even though you're not polluting as much per minute while you're waiting to get through the light, you have to add all that wait time to the total amount of pollution emitted on your regular trip to work.

By eliminating the congestion you can reduce that "extra" pollution that occurs simply from all the waiting. Not only that but we'll also be taking all those cars off the road. So we get the reduced pollution from having fewer cars on the road as the conclusion would suggest, but also we get less pollution per vehicle since they're no longer stuck in traffic.

What do you think?

[kaseyb002]

To me, if they hadn't included the part about nonmoving vehicles emitting half as much pollution, the question would have been much easier.

I assume that little extra-part is meant purely for distraction right?

[ManhattanPrepLSAT1]

No, no! That's an essential part of the argument. If non-moving vehicles emit half as much pollution as moving vehicles then if you have tons of traffic, non-moving vehicles will still be polluting even though you aren't making any progress on getting to your destination.

Imagine, you're driving from your home to your office. Along the way you get stuck for 15 minutes in really bad traffic and don't move at all. According tot he stimulus you'd pollute more than if you simply drove to work and hit no traffic at all.

This helps us with the idea that taking cars off the road will reduce pollution!

[kaseyb002]

Sorry I should have been more specific. The "half as much" part is what threw me off. I see clearly how the fact that nonrunning vehicles pollute is essential. (and after your reading your past, I can also see how it needs to be compared to "normal" or running vehicles in order to make it more concrete).

But to me, if it read, "Nonrunning vehicles pollute" without it being less than running vehicles it would have been easier for me at least. Perhaps I'm still missing some subtle point about it though.

[ManhattanPrepLSAT1]

Strengthen questions don't ask for an answer choice that is necessary to the argument but that makes the conclusion more likely to be true. So for #9 we may not need the answer choice to be so specific, but for #10 anything that makes the conclusion more likely to be true would be correct. We may not need nonmoving vehicles to pollute half as much as moving vehicles, but if they do that would support the conclusion, right?

Hope that helps!

[Mw22390]

Let's make it personal. Suppose you drive to work each day, and that commute would take you 20 minutes if you could drive it at midnight. But during the morning you're fighting with everyone else who wants to share the road with you. Suppose at 9am that same trip takes you 45 minutes because at this one stoplight you have to sit and wait for 25 minutes in a backup.

Would a car going 60 mph give off the same emissions as a car going 5 mph in congested traffic, according to answer B?

[WaltGrace1983]

I thought I'd add my own analysis to (B).

If walk, one less vehicle than there would be otherwise
→
If people walk when feasible, pollution is greatly reduced

The assumption here is that the one less vehicle would not be offset by other pollution-inducing things. For example, let's say I usually drive to work but I decided to walk. Well what if I have a carpool, then what happens? Maybe they all drive to work. Or perhaps when I walk to work, I like to dump toxic waste into the air because that's just how I roll. So the way that I initially saw this question was to rule out deleterious consequences.

(B) does this, just in a less-than-obvious way. (B) basically says...

(the more the congestion) → (more nonmoving vehicles)
(more nonmoving vehicles) → (1/2 as much pollution per second).

So what is going on here then? Well, a traffic jam - though emitting half as much pollution per second - will cause a lot longer timeframe (more seconds) of emitting pollution. Thus, not only would congestion NOT "greatly reduce" the amount of pollution, it may even increase the amount of pollution.

So what does this mean? Why does this strengthen?

This strengthens because we know that if "the greater the congestion is, the more nonmoving running vehicles," we simultaneously know that the less the congestion, the less nonmoving vehicles. This gives us one reason to believe that people walking (i.e. creating less congestion) would "greatly reduce" the pollution.

Hope that is simple to understand

[rikky.brown]

I was stuck between A and B because I thought the contrapositive of A sounded better than the way B sounded in its present form. Can you clarify what the contrapositive is for A?

[maryadkins]

(A) would be diagrammed:

AP who never drive would walk instead of ride --> Not fewer vehicles on the road

The contrapositive would be

Fewer vehicles on the road --> There are still APs who ride

[rpcuhk]

(C) is irrelevant. That some cars pollute more than others doesn't help us in reducing pollution because we don't know which cars we will be taking off the road, if we choose to walk rather than drive.

I'm still confused about (C)
Although we don't know if we are taking off the more polluted cars , (C) does suggest that dirve=pollute, thus less driver = less pollution. Isn't this a strengthener?

[Mab6q]

(C) is irrelevant. That some cars pollute more than others doesn't help us in reducing pollution because we don't know which cars we will be taking off the road, if we choose to walk rather than drive.

I'm still confused about (C)
Although we don't know if we are taking off the more polluted cars , (C) does suggest that dirve=pollute, thus less driver = less pollution. Isn't this a strengthener?

C is incorrect because it adds nothing to the reasoning between our premise and conclusion. It essentially is saying that if I drive a gas guzzling truck and you drive a 4 cylinder Honda, I will make a greater contribution to lowering pollution prevention because my truck would have used more gas than your Honda.

Does that strengthen our relationship, no! It adds nothing new. We could infer that from the original argument.

[michaelwcarper]

I thought I'd add my own analysis to (B).

If walk, one less vehicle than there would be otherwise
→
If people walk when feasible, pollution is greatly reduced

The assumption here is that the one less vehicle would not be offset by other pollution-inducing things. For example, let's say I usually drive to work but I decided to walk. Well what if I have a carpool, then what happens? Maybe they all drive to work. Or perhaps when I walk to work, I like to dump toxic waste into the air because that's just how I roll. So the way that I initially saw this question was to rule out deleterious consequences.

(B) does this, just in a less-than-obvious way. (B) basically says...

(the more the congestion) → (more nonmoving vehicles)
(more nonmoving vehicles) → (1/2 as much pollution per second).

So what is going on here then? Well, a traffic jam - though emitting half as much pollution per second - will cause a lot longer timeframe (more seconds) of emitting pollution. Thus, not only would congestion NOT "greatly reduce" the amount of pollution, it may even increase the amount of pollution.

So what does this mean? Why does this strengthen?

This strengthens because we know that if "the greater the congestion is, the more nonmoving running vehicles," we simultaneously know that the less the congestion, the less nonmoving vehicles. This gives us one reason to believe that people walking (i.e. creating less congestion) would "greatly reduce" the pollution.

Hope that is simple to understand

Thanks. The "half as much pollution" is essentially a red herring. If it wasn't included, B would strengthen even more. But as long as a nonmoving car, due to congestion, emits some pollution, then there is some potential pollution that can be eliminated with fewer cars.

Now, if nonmoving cars could somehow replace moving cars, then this answer would be wrong, because nonmoving cars pollute less. But if a car is driving a distance, time spent non-moving in congestion is wasted. Any time spent non-moving in congestion, emitting half the normal pollution, is simply going to be added to the moving time. Minimizing pollution means no congestion, and no non-moving cars. Non-moving and moving are not equivalent: moving is necessary, and non-moving is not.

And since the answer tells us that # of cars causes congestion, then reducing cars will also reduce pollution.