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Difficulty: EasyPrimary Purpose of the Whole Text

In the eighteenth century, marine navigation faced a major obstacle: sailors could not accurately determine their longitude at sea, leading to costly and dangerous shipwrecks. The British Parliament offered a massive financial reward to anyone who could solve this issue. While astronomers argued that mapping the moon and stars was the only viable path, self-taught clockmaker John Harrison proposed a mechanical solution. Harrison designed and built the H4, a highly precise marine chronometer that could maintain accurate time despite the motion of a ship and changes in temperature. Ultimately, Harrison’s invention revolutionized navigation, proving that mechanical timekeeping was superior to astronomical observations for determining location at sea.

Which choice best states the main purpose of the text?

  1. A
    To argue that mechanical inventions are generally more valuable to society than theoretical science.
  2. B
    To detail the financial rewards offered by the British Parliament to eighteenth-century inventors.
  3. To describe how John Harrison's invention of a precise marine chronometer solved a major navigation problem.Answer
  4. D
    To explain the specific astronomical formulas sailors used to calculate their position before the chronometer.

Answer

To describe how John Harrison's invention of a precise marine chronometer solved a major navigation problem.
The correct answer correctly identifies that the primary purpose of the passage is to explain how John Harrison developed a mechanical marine chronometer to resolve a critical navigational challenge (finding longitude at sea). The text outlines the problem (lack of accurate longitude tracking), the competing ideas (astronomy vs. mechanical), and the successful resolution (Harrison's H4 chronometer revolutionizing navigation).

Step-by-Step Solution

1
Analyze the beginning of the passage to identify the central problem introduced.
The text begins by identifying a major obstacle in eighteenth-century navigation: the inability of sailors to accurately determine longitude, which caused dangerous shipwrecks.
Understanding the initial conflict helps determine the overarching goal of the narrative.
2
Examine the middle and end of the passage to identify the solution and its impact.
The text describes how John Harrison built the H4 chronometer to solve the longitude problem, and how his mechanical invention ultimately revolutionized navigation by outperforming astronomical methods.
Identifying the resolution of the conflict helps determine the main message or purpose of the text.
3
Synthesize the findings to match with the correct option.
The primary purpose of the text is to show how Harrison's invention solved the navigation problem of determining longitude at sea, which aligns with the correct option.
Ensuring the choice summarizes the whole text rather than focusing on secondary details like the British Parliament's reward or a general claim about engineering vs. science.

Key Concept

Identifying the primary purpose of a passage requires summarizing the main narrative or argumentative arc of the entire text, distinguishing between the central focus and secondary details.
Estimated Time:50s
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Topics

Primary Purpose of the Whole Text

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