2014 AMC 10A Problem 18
Attempt Problem 18 of the 2014 AMC 10A below, then check your answer against the professionally curated solution from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 2014 AMC 10A solutions, or check the answer key.
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18.
A square in the coordinate plane has vertices whose -coordinates are and What is the area of the square?
Answer: B
Solution:
Opposite vertices of a square have the same average -coordinate. Thus the opposite pairs must have -coordinates and , the two pairs with equal sum. In particular, a vertex with -coordinate is adjacent to vertices with -coordinates and .
Let one vertex be , and let its adjacent vertex with -coordinate be with .
Rotating the side vector by gives the next side vector , so another vertex has y-coordinate . The remaining y-coordinates are and , hence .
The side length squared is , which is the area of the square.
Thus, B is the correct answer.
Problem 18 in Other Years
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