Problem: Hydropower is produced in 150 countries, with the Asia-Pacific region generating 32 percent of global hydropower in 2010. China is the largest hydroelectricity producer, with 721 terawatt-hours of production in 2010, representing around 17 percent of domestic electricity use. There are now three hydroelectricity plants larger than 10 GW: the Three Gorges Dam in China, Itaipu Dam across the Brazil/Paraguay border, and Guri Dam in Venezuela. The cost of hydroelectricity is low, making it a competitive source of renewable electricity. The average cost of electricity from a hydro plant larger than 10 megawatts is 3 to 5 U.S. cents per kilowatt-hour.
What is the average cost of electricity from a hydro plant smaller than 10 megawatts?
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Answer: unanswerable


Problem: In 2010, Boston was estimated to have 617,594 residents (a density of 12,200 persons/sq mile, or 4,700/km2) living in 272,481 housing units— a 5% population increase over 2000. The city is the third most densely populated large U.S. city of over half a million residents. Some 1.2 million persons may be within Boston's boundaries during work hours, and as many as 2 million during special events. This fluctuation of people is caused by hundreds of thousands of suburban residents who travel to the city for work, education, health care, and special events.
About what was the population of Boston in 2010?
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Answer: 617,594


Problem: Antarctica has no indigenous population and there is no evidence that it was seen by humans until the 19th century. However, belief in the existence of a Terra Australis—a vast continent in the far south of the globe to "balance" the northern lands of Europe, Asia and North Africa—had existed since the times of Ptolemy (1st century AD), who suggested the idea to preserve the symmetry of all known landmasses in the world. Even in the late 17th century, after explorers had found that South America and Australia were not part of the fabled "Antarctica", geographers believed that the continent was much larger than its actual size.
What is the vast continent in the far north?
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Answer:
unanswerable