1986 AMC 8 Problem 21
Below is the professionally curated solution for Problem 21 of the 1986 AMC 8, from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 1986 AMC 8 solutions, or check the answer key.
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Difficulty rating: 1220
21.
Suppose one of the eight lettered identical squares is included with the four shaded squares in the T-shaped figure shown. How many of the resulting figures can be folded into a topless cubical box?
Solution:
The four shaded squares fold into four faces of an open box, and the added square supplies the fifth face. Picturing the folds, the squares and each complete a valid topless box.
The squares and do not work, because folding would force four faces to meet at a single corner. That leaves valid figures.
Thus, the correct answer is E .
Problem 21 in Other Years
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