1991 AMC 12 Problem 29
Attempt Problem 29 of the 1991 AMC 12 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 1991 AMC 12 solutions, or check the answer key.
All problems are used with official legal permission of the Mathematical Association of America (MAA).
29.
Equilateral triangle has been creased and folded so that vertex now rests at on as shown. If and then the length of crease is
Answer: B
Small hint:
A fold crease is the perpendicular bisector of the segment joining a point to its image
Big hint:
Place and
Solution:
With the coordinates in the hint, the perpendicular-bisector condition for is which simplifies to Intersecting this line with gives Intersecting it with gives Hence
Thus the correct answer is B.
Problem 29 in other years
- 1950 AMC 12
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