Unplugged Practice Test: Logical Reasoning Set 2, Question 2 (Weaken)
Taking the test? Finish it first. This page shows the answer.
- Weaken questions ask which new fact most undermines the argument.
- Find the gap the argument leaves open, then look for the choice that widens it.
- Every question on this test is original, written to the same logical skeletons as real questions, and Steve checked every one himself before release.
The question
Hollings: Quarries that bore blast holes with steel-tipped bits could bore them with diamond-matrix bits instead. Diamond-matrix bits vibrate far less in the operator's hands and throw off much less rock dust. On several kinds of stone they also cut a hole in about half the time. Quarry managers should therefore start boring with diamond-matrix bits. Arriaga: A diamond-matrix bit costs 8 times what a steel-tipped bit costs, so boring with them is not a practical option for quarry managers now.
2. Which one of the following, if true, would give Hollings the strongest response to Arriaga's objection?
- (A)A diamond-matrix bit can be reground and reused dozens of times, whereas a steel-tipped bit is scrapped after one hole.
- (B)The price of drilling bits is one among the many costs that a quarry manager has to cover each year.
- (C)Techniques for holding down rock dust at a quarry without wetting the stone have become available in the past few years.
- (D)Quarry managers have long been willing to take up any change that shortens the time needed to bore a hole.
- (E)Some managers will pay extra for equipment that they can point to when neighbors complain about conditions at the quarry.
AWhy (A) is correct
Arriaga treats the sticker price as the whole cost of switching bits. (A) undercuts that: if a diamond-matrix bit can be reground and reused dozens of times while a steel-tipped bit gets thrown away after one hole, the 8 times price spreads across many holes, so diamond bits need not cost more per hole at all. That removes Arriaga's practicality objection at the root.
Why the other answers are wrong
BWhy (B) is wrong
(B) only notes that bit price is one of many yearly costs, which doesn't erase an 8 times price gap.
CWhy (C) is wrong
(C) points to dust-control methods that don't involve bits, so the price objection stands untouched.
DWhy (D) is wrong
(D) shows managers have long been willing to take up time-saving changes, not whether today's price makes diamond bits impractical.
EWhy (E) is wrong
(E) says some managers pay extra to satisfy neighbors, but an 8 times markup is well beyond extra, so it doesn't answer Arriaga's point.
Common questions
What type of question is this?
Weaken. Weaken questions ask which new fact most undermines the argument.
How do I get better at Weaken questions?
Find the gap the argument leaves open, then look for the choice that widens it. The free LSAT cheat sheet lists the wrong-answer patterns to watch for on every type.
