Logical Reasoning · Necessary Assumption

PrepTest 142 · Section 2 · Question 16

Phase 1 (your first ~400 questions): read the guidance, then answer. No clock.

Step 1 · Pre-Question Guidance · read this first

Question type

Necessary Assumption

The one idea it tests

A plan that promises to save money by cutting one cost quietly assumes the new cost of the plan does not eat up the savings.

The basic logic

The argument shows a device, a wasted resource, and a smaller bill if the two are joined, then jumps to 'so we save money.' Smaller bills only mean savings if what you spend to get them is less. Pull the Plank: if the device costs more than it saves, the money conclusion falls.

Tiny words that decide it

“thereby”
“if”
“saving”

Playground logic

Owen says the school could feed its scrap paper into a notebook gadget, buy fewer notebooks, and so save money. The hidden sauce: the notebook savings are at least as big as what the gadget costs. Pull that plank and 'save money' collapses.

Step 2 · The kid story

Owen's Paper Plan

Owen burst into the classroom with a flyer. "Ms. Rivera! This gadget mashes scrap paper into brand-new notebooks. Our recycling bin overflows every day. So if we fed our scrap into the gadget, we'd buy way fewer notebooks. We'd save money!" Ms. Rivera smiled. "Lovely. One question." Lulu was already writing on her clipboard. "How much is the gadget?" Owen checked the flyer. "Uh... nine hundred dollars." Priya sipped her juice box. "We spend about forty dollars a year on notebooks. Even if we never bought another one, it would take over twenty years to make that back." Kevin gasped. "By then I'll be a real paleontologist!" Owen folded the flyer. "So buying fewer notebooks is not the same as saving money." "Not if the gadget costs more than you save," said Lulu.

Step 3 · Try the model question

Owen: The paper-mashing gadget turns scrap paper into notebooks. Our school throws away piles of scrap every day. So if the school fed its scrap into the gadget, it would buy far fewer notebooks, and so it would save money.

Owen's argument relies on which one of the following assumptions?

Step 4 · The courtroom tale

The Pond-Cooled Bakery

A bakery sued its landlord to let it install a pond-water cooling machine. The bakery's lawyer said, "This machine cools ovens with pond water. There's a pond out back. So with the machine, our air-conditioning bill would drop, and we'd save money." Mr. Whitfield, for the landlord, rose. "Your Honor, the machine costs fifty thousand dollars. The bill would drop by two hundred a year." The judge did the math on a napkin. "Counselor, a smaller bill is not savings if the cure costs more than the illness. Your argument assumes the drop pays for the machine." The bakery's lawyer quietly turned on a small desk fan.

Step 5 · Work the real question

Open PrepTest 142, Section 2, Question 16 in your official copy from LSAC (for example in LawHub) and read it there.

Your answer

How to apply it

Find the plan and its promised payoff. Notice the last step: a smaller bill is turned into 'saving money.' Ask what that step quietly needs. Use Pull the Plank on each choice: if it were false, would the money conclusion fall apart? Be wary of choices demanding the plan be the best of all options or about who uses the resource, since the argument never needs those.