1989 AMC 8 Problem 11
Attempt Problem 11 of the 1989 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 1989 AMC 8 solutions, or check the answer key.
All problems are used with official legal permission of the Mathematical Association of America (MAA).
11.
Which of the five “T-like shapes” would be symmetric to the one shown with respect to the dashed line?
Answer: B
Small hint:
Two figures are symmetric across the dashed line when folding the paper along that line makes one land exactly on the other
Big hint:
A reflection across a vertical line keeps top and bottom fixed but swaps left and right; track where the small corner square ends up and how the slanted strokes turn
Solution:
Two figures are symmetric with respect to the dashed line when folding the paper along that line makes one coincide with the other. Reflecting across the vertical dashed line swaps left and right while leaving top and bottom unchanged.
Under this reflection the small square in the top-left corner moves to the top-right corner, the straight crossbar reverses its slant, and the stem that points down and to the right must instead point down and to the left. Only one choice has all three of these features.
Thus, the correct answer is B .
Problem 11 in other years
- 1985 AMC 8
- 1986 AMC 8
- 1987 AMC 8
- 1988 AMC 8
- 1990 AMC 8
- 1991 AMC 8
- 1992 AMC 8
- 1993 AMC 8
- 1994 AMC 8
- 1995 AMC 8
- 1996 AMC 8
- 1997 AMC 8
- 1998 AMC 8
- 1999 AMC 8
- 2000 AMC 8
- 2001 AMC 8
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