2022 AMC 8 Problem 18

Attempt Problem 18 of the 2022 AMC 8 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 2022 AMC 8 solutions, or check the answer key.

All problems are used with official legal permission of the Mathematical Association of America (MAA).

18.

The midpoints of the four sides of a rectangle are (−3,0),(-3, 0), (2,0),(2, 0), (5,4),(5, 4), and (0,4).(0, 4). What is the area of the rectangle?
2020
2525
4040
5050
8080
Answer: C
Concepts:coordinate geometryparallelogrammidpoint
Small hint:
The given midpoints form a parallelogram inside the rectangle
Big hint:
The midpoint parallelogram has half the area of the original rectangle
Solution:
The four given midpoints form a parallelogram. Its horizontal base has length 2−(−3)=52-(-3)=5, and its height is 44, so its area is 5⋅4=205\cdot4=20.
For any rectangle, the parallelogram formed by joining the side midpoints has half the area of the rectangle. Therefore the rectangle’s area is 2⋅20=402\cdot20=40.
Thus, the correct answer is C.
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