Logical Reasoning

PT17 · S3 · Q2 A certain type of insect trap uses

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A certain type of insect trap uses a scented lure to attract rose beetles into a plastic bag from which it is difficult for them to escape.

Fact 1

Several rose-beetle traps in a garden greatly reduce the rose-beetle population.

Fact 2

One trap by itself actually increases the rose-beetle population.

Evaluate

Why would a single trap make things worse, but several traps make things much better? The trap uses a scented lure that attracts beetles. If the lure attracts more beetles than a single trap can capture, the garden ends up with extra beetles roaming free. If multiple traps are present, the lure is still pulling beetles in, but now there is enough trapping capacity to actually catch them.

Goal

The correct answer should explain how the same lure-and-trap system creates the opposite outcome at different scales — by clarifying what changes when the number of traps changes.

2.

Which one of the following, if true, most helps to resolve the apparent discrepancy?

  1. The scent of a single

    No Distinction

    If a single lure cannot reach all beetles in the garden, that suggests one trap should attract fewer beetles than several traps would — but it does not explain why a single trap increases the population. If the lure does not reach distant beetles, those beetles should be unaffected, not multiplied. This does not resolve the paradox.

    4% picked this

  2. Several traps are better able

    Restates Paradox

    This just confirms that several traps catch more beetles than one trap does — which is part of what we already knew, since several traps reduce the population while one increases it. It does not explain why one trap actively makes things worse. Catching fewer is not the same as causing an increase.

    10% picked this

  3. When there are several traps

    Cheats Paradox

    If anything, this deepens the puzzle. If each of several traps catches fewer beetles than a lone trap would, then a single trap must be efficient at capture. So why does that efficient single trap leave the garden with more beetles? This answer makes the one-trap problem harder to explain, not easier.

    1% picked this

  4. Correct

    The presence of any traps

    Why this is right

    This is the explanation. The lure attracts more beetles than one trap can capture — meaning one trap pulls in beetles from outside the garden but cannot catch them all, leaving the surplus loose in the garden. Several traps will not attract significantly more beetles than one trap (the lure's drawing power is roughly fixed), but they provide enough capture capacity to actually catch the beetles that get drawn in. So adding traps does not multiply the attraction; it multiplies the capture. Result: with one trap, attraction outpaces capture and the population rises; with several, capture catches up and the population falls.

    Skill tested: Paradox · how this choice captures the argument's function is the move to repeat next time.

    69% picked this

  5. When there is only one

    No Distinction

    Even if one trap's bag fills up and lets some beetles escape, those escapees were beetles that had already been in the garden (they were attracted by the lure but not held by the bag). This explains why a single trap might be less effective than expected, but it does not explain why the population rises beyond what it would have been with no trap. The increase needs an outside source of beetles — namely, beetles attracted in by the lure from outside the garden.

    15% picked this

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