Problem:
Suppose one of the eight lettered identical squares is included with the four squares in ' the T-shaped figure outlined. How many of the resulting figures can be folded into a topless cubical box?
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Answer Choices:
A.  
B.  
C.  
D.  
E.  
Solution:
Label the four squares in the T-shaped figure as shown. First think of as the base of the cube. Then will be three of the "sides" and the fourth side could be , or . Now think of as the base. Then are three sides and , or could be the fourth side. and are not possible because four sides of a cube cannot come together at a point.

Answer: .
The problems on this page are the property of the MAA's American Mathematics Competitions