instruction:
Answer the question from the given passage. Your answer should be directly extracted from the passage, and it should be a single entity, name, or number, not a sentence.
question:
Passage: The most useful instrument for analyzing the performance of steam engines is the steam engine indicator. Early versions were in use by 1851, but the most successful indicator was developed for the high speed engine inventor and manufacturer Charles Porter by Charles Richard and exhibited at London Exhibition in 1862. The steam engine indicator traces on paper the pressure in the cylinder throughout the cycle, which can be used to spot various problems and calculate developed horsepower. It was routinely used by engineers, mechanics and insurance inspectors. The engine indicator can also be used on internal combustion engines. See image of indicator diagram below (in Types of motor units section). Question: What year saw the earliest recorded use of the steam engine indicator?
answer:
1851


question:
Passage: There were 158,349 households, of which 68,511 (43.3%) had children under the age of 18 living in them, 69,284 (43.8%) were opposite-sex married couples living together, 30,547 (19.3%) had a female householder with no husband present, 11,698 (7.4%) had a male householder with no wife present. There were 12,843 (8.1%) unmarried opposite-sex partnerships, and 1,388 (0.9%) same-sex married couples or partnerships. 35,064 households (22.1%) were made up of individuals and 12,344 (7.8%) had someone living alone who was 65 years of age or older. The average household size was 3.07. There were 111,529 families (70.4% of all households); the average family size was 3.62. Question: How many households has kids under the age of 18 living in them?
answer:
68,511


question:
Passage: In the laboratory, stratigraphers analyze samples of stratigraphic sections that can be returned from the field, such as those from drill cores. Stratigraphers also analyze data from geophysical surveys that show the locations of stratigraphic units in the subsurface. Geophysical data and well logs can be combined to produce a better view of the subsurface, and stratigraphers often use computer programs to do this in three dimensions. Stratigraphers can then use these data to reconstruct ancient processes occurring on the surface of the Earth, interpret past environments, and locate areas for water, coal, and hydrocarbon extraction. Question: What type of surveys show the location of stratigraphic units in the subsurface?
answer:
geophysical