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VerbalCritical Reasoning

Free GMAT Critical Reasoning Practice Question

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Brackenfield Markets, a regional grocery chain, recently installed self-checkout machines in all of its stores. The company's data show that an individual self-checkout transaction is completed somewhat faster, on average, than an individual transaction handled at a staffed checkout lane. Even so, in the months after the machines were installed, the average time that a customer spent waiting to check out at a Brackenfield store did not fall at all. This outcome, however, is not surprising, because, when the machines were installed, ___

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Answer & Explanation

Correct answer

C

This is a complete-the-passage item. The connector is the word "because," so the blank must supply the reason that makes the puzzling result logical. The puzzle is this: each self-checkout transaction is faster, yet the average time a customer spends waiting did not fall at all. The credited choice has to explain why faster individual transactions failed to produce shorter overall waits.

(C) does exactly that. Overall waiting time depends on total throughput, meaning how many customers the whole front end of the store can process per hour, not on how fast any single transaction is. If the store removed several staffed lanes to make room for the self-checkout machines, the machines replaced checkout capacity rather than adding to it. The time saved on each faster transaction was offset by the capacity lost when those staffed lanes were removed, so the front end's total throughput, and with it the average wait, stayed roughly the same. Plugged into "because," (C) makes the flat wait time the expected result, and it is the only completion the argument logically requires.

The correct answer is (C).