Here is a question about this article: The late nineteenth century also brought the systematic study of color theory, and particularly the study of how complementary colors such as red and green reinforced each other when they were placed next to each other. These studies were avidly followed by artists such as Vincent van Gogh. Describing his painting, The Night Cafe, to his brother Theo in 1888, Van Gogh wrote: "I sought to express with red and green the terrible human passions. The hall is blood red and pale yellow, with a green billiard table in the center, and four lamps of lemon yellow, with rays of orange and green. Everywhere it is a battle and antithesis of the most different reds and greens."
What is the answer to this question: When did the systematic study of color theory begin?
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So... late nineteenth century

Here is a question about this article: Ancient Egypt made significant advances in astronomy, mathematics and medicine. Their development of geometry was a necessary outgrowth of surveying to preserve the layout and ownership of farmland, which was flooded annually by the Nile river. The 3-4-5 right triangle and other rules of thumb were used to build rectilinear structures, and the post and lintel architecture of Egypt. Egypt was also a center of alchemy research for much of the Mediterranean.The Edwin Smith papyrus is one of the first medical documents still extant, and perhaps the earliest document that attempts to describe and analyse the brain: it might be seen as the very beginnings of modern neuroscience. However, while Egyptian medicine had some effective practices, it was not without its ineffective and sometimes harmful practices. Medical historians believe that ancient Egyptian pharmacology, for example, was largely ineffective. Nevertheless, it applies the following components to the treatment of disease: examination, diagnosis, treatment, and prognosis, which display strong parallels to the basic empirical method of science and according to G. E. R. Lloyd played a significant role in the development of this methodology. The Ebers papyrus (c. 1550 BC) also contains evidence of traditional empiricism.
What is the answer to this question: What theory did the Egyptians use to build rectilinear structures?
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So... The 3-4-5 right triangle

Here is a question about this article: As of the Census of 2010, there were 1,307,402 people living in the city of San Diego. That represents a population increase of just under 7% from the 1,223,400 people, 450,691 households, and 271,315 families reported in 2000. The estimated city population in 2009 was 1,306,300. The population density was 3,771.9 people per square mile (1,456.4/km2). The racial makeup of San Diego was 45.1% White, 6.7% African American, 0.6% Native American, 15.9% Asian (5.9% Filipino, 2.7% Chinese, 2.5% Vietnamese, 1.3% Indian, 1.0% Korean, 0.7% Japanese, 0.4% Laotian, 0.3% Cambodian, 0.1% Thai). 0.5% Pacific Islander (0.2% Guamanian, 0.1% Samoan, 0.1% Native Hawaiian), 12.3% from other races, and 5.1% from two or more races. The ethnic makeup of the city was 28.8% Hispanic or Latino (of any race); 24.9% of the total population were Mexican American, and 0.6% were Puerto Rican.
What is the answer to this question: In 2009, what percentage of the population was Hispanic?
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So...
28.8%