PT70.S1.Q24 - many homeowners regularly add commercial fertilizers

Edmond.DantesEdmond.Dantes Alum Member
edited May 2016 in Logical Reasoning 154 karma
https://7sage.com/lsat_explanations/lsat-70-section-1-question-24/
I ran into some issues with a LR question on PT 70 S1 and would love some inputs from other students here. I chose E, which is the wrong answer, but I'm not at all sure why I am wrong.

For #24 (the Macro/Micronutrients question), the last sentence reads:

"To remain healthy in the long run, soils for lawns require the presence of these macronutrients and also trace amounts of micronutrients...which are depleted when grass clippings are raked up..."

Isn't this a conditional claim?

Healthy --> Macro + Micro, and

Grass Clips Raked --> Micro Depleted

Assuming that IF micronutrients are there, THEN it's NOT depleted (which is very reasonable to me), then taking the contrapositive, we can connect the two:

Healthy --> Macro + (Micro --> /MicroDepleted --> /GrassClipsRaked)

(Sorry for the visual representation. Couldn't get the format to look right. But Healthy is connected to Macro AND Micro, and Micro is itself connected to the rest of the chain).

So if you deny the last necessary condition, then you should be able to work your way back. So if Grass Clips are raked, then Micro Depleted, then /Micro (micronutrients are gone), then /Healthy.

I thought E communicated exactly this: "Homeowners who rake up their grass clippings are unable to maintain the long-term health of the soils in their lawns and gardens," which in lawgic is

Grass Clips Raked --> /Healthy

which to me is exactly as above. Where am I wrong?

Comments

  • quinnxzhangquinnxzhang Legacy Member
    edited May 2016 611 karma
    @Edmond.Dantes said:
    Grass Clips Raked --> Micro Depleted
    The stimulus doesn't allow us to conclude this. Grass clippings are one way to get micro-nutrients, but the stimulus doesn't say it's the ONLY way. Thus, when the grass clippings are raked up, this CAN deplete the micro-nutrients in the soil, but it doesn't HAVE to. If there is some other way to get micro-nutrients, then raking up the grass clippings wouldn't necessarily deplete the micro-nutrients.

    And the stimulus does leave open the possibility that, say, there are some rare fertilizers that contain all the macro- and micro-nutrients necessary for long-term health. Thus, the stimulus leaves open the possibility that someone can rake their clipped grass, but use this rare fertilizer to provide all the micro-nutrients needed.
  • Edmond.DantesEdmond.Dantes Alum Member
    edited May 2016 154 karma
    @quinnxzhang said:
    The stimulus doesn't allow us to conclude this.
    Thanks for the comment. I thought the last sentence covered this?

    "micronutrients...which are depleted when grass clippings are raked up..."

    Another way to say that is "when grass clippings are raked up, micronutrients are depleted."

    Isn't that a conditional statement?
  • quinnxzhangquinnxzhang Legacy Member
    edited May 2016 611 karma
    @Edmond.Dantes said:
    "when grass clippings are raked up, micronutrients are depleted."
    I think there's a fork in the road for how we should interpret the consequent of your proposed conditional, and depending on how we interpret your consequent, the conditional is either unsupported or else subtly irrelevant.

    If we interpret "micro-nutrients are depleted" to mean something like "micro-nutrients are depleted forever", then the conditional is simply unsupported. The stimulus leaves open the possibility that you can supplement your lawn with something else that contains micro-nutrients. This is the interpretation my first comment was addressing.

    If we interpret "micro-nutrients are depleted" to mean something like "micro-nutrients are depleted temporarily", then the conditional is true (maybe), but also irrelevant. Say you rake up the clippings and the micro-nutrients deplete in the next hour. But suppose you then add all the micro-nutrients needed for lawn health by using a rare fertilizer. Well, now the lawn has all the nutrients needed for long-term health, so (E) is false. That is to say, it's possible for both the micro-nutrients to get depleted and then get replenished, so the conditional here is irrelevant long-term lawn health.

  • Edmond.DantesEdmond.Dantes Alum Member
    edited May 2016 154 karma
    @quinnxzhang said:
    the conditional is either unsupported or else subtly irrelevant.
    Ah, there's the rub.

    The key problem is the assumption: Micro Depleted --> No Micro, because "No Micro" could mean "long enough to harm health" or "for a second." In this case, it means "for a second." If micro is depleted, then temporarily, there is no micro.

    However, in the context of "No Micro --> /Health," the "No Micro" means "long enough to harm health," which is a rather different.

    Not sure why this wasn't apparent at the time. I was really focused on the group one logic indicator. Thanks a bunch. I appreciate the quick response.

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