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Information and IdeasVery hardInferring location of a change from metered gaps

Information and Ideas practice question

An apartment building is billed from a master meter at the street, but each of its 60 units also has its own meter. The gap between the master reading and the sum of the unit readings accounts for irrigation, the laundry room, and any leaks in the shared pipes. For years the master meter read about 180,000 gallons a month while the unit meters summed to roughly 162,000. This spring the master meter read 258,000 gallons and the unit meters summed to 164,000. Occupancy records show no change in the number of residents. From these readings the manager can reasonably conclude that ______

Which choice most logically completes the text?

  1. A. nearly all of the additional consumption is occurring somewhere other than inside the individual apartments.Correct
  2. B. residents have sharply increased the amount of water they use in their apartments.
  3. C. irrigation, laundry, and shared-pipe losses now account for more than half of the building's total water use.
  4. D. the master meter at the street has begun to overstate the building's consumption.

Answer: A. nearly all of the additional consumption is occurring somewhere other than inside the individual apartments.

Unit-metered use went from 162,000 to 164,000 gallons—essentially flat—while the master reading rose by 78,000. Almost the entire increase therefore falls in the unmetered gap, which by definition lies outside the apartments. B contradicts the unit readings, which rose by only about 1 percent. C is an arithmetic error: the gap is 258,000 minus 164,000, or 94,000 gallons, about 36 percent of the total, not more than half. D dismisses the one category the passage explicitly defines—the master meter is supposed to exceed the unit sum, and a growing gap is fully explained by irrigation, laundry, or a shared-pipe leak, so malfunction is unsupported speculation.

Why the other answers are wrong

B. residents have sharply increased the amount of water they use in their apartments.
The unit meters rose only from 162,000 to 164,000 gallons — about 1 percent — so residents' in-apartment use was essentially flat.
C. irrigation, laundry, and shared-pipe losses now account for more than half of the building's total water use.
The gap is 258,000 − 164,000 = 94,000 gallons, which is about 36 percent of the 258,000 total, not more than half.
D. the master meter at the street has begun to overstate the building's consumption.
The master meter is supposed to read higher than the unit sum; the passage names irrigation, laundry, and shared-pipe leaks as the explanation for the gap, so a malfunction is speculation the readings don't support.

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