Passage: A survey of a large office building found that after motion-sensor switches were fitted to the corridor lights, the building's total electricity consumption fell by only 3 per cent, although corridor lighting had earlier accounted for 15 per cent of that consumption. No other change was made to the building's electricity use. Which of the following can most reasonably be inferred?

Question

Accepted Answer

The corridor lights continued to be switched on for most of the time even after the sensors were fitted. Corridor lighting fell from 15 per cent of consumption to 12 per cent, a drop of only one-fifth of its earlier level, so the corridors were still drawing about four-fifths as much power as before — the lights were on most of the time. A total failure of the sensors would have produced no saving at all, so the first option is ruled out; the remaining options are recommendations or facts the passage never supplies.

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