PrepTest 136, Section 2, Question 22

What we’re looking for

Working the answers

• A

  Sixty becoming thirty is certainly a reduction by half. But the answer attaches that reduction to each individual runway, while the passage attaches it to the entire airport.

  Imagine two runways each handling thirty planes an hour in good weather. In poor weather, only one operates, still handling thirty. The airport's total falls from sixty to thirty even though the operating runway's rate doesn't fall at all. Those aren't claimed facts about this airport; they show why the overall figures don't establish the per-runway claim.

• B

  Being allowed to use adjacent runways together doesn't tell us how likely simultaneous landings are at any given moment. The allowance is a rate over an hour, not a report of what happens at every instant. B adds timing information we don't have.

• C

  The problem is the restriction on simultaneous use in poor visibility. Using runways together in suitable conditions helps the airport accommodate more arrivals. The passage doesn't say simultaneous use itself creates serious delays, much less that using any two runways does so.

• D
  Correct

  The schedules assume good weather, and good weather permits sixty landings an hour. The airlines are therefore planning on permission for more than thirty landings an hour. This stays at the airport-wide level the evidence describes. It doesn't claim a particular landing rate for each runway.

• E

  Weather isn't the only possible source of delays. A plane might need an engine part even on a clear day, leaving its flight seriously delayed. Explaining why bad weather creates delays doesn't establish that good weather leaves few or no serious delays.