1993 AMC 8 Problem 25
Below is the professionally curated solution for Problem 25 of the 1993 AMC 8, from LIVE by Po-Shen Loh. You can also try the full timed exam, view all 1993 AMC 8 solutions, or check the answer key.
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Difficulty rating: 1270
25.
A checkerboard consists of one-inch squares. A square card, inches on a side, is placed on the board so that it covers part or all of the area of each of squares. The maximum possible value of is
or
or
or
or
or more
Solution:
Tilt the card and center it on a corner where four grid squares meet, as shown. Because the card's diagonal, is longer than each of the four corners of the card reaches past a grid line into the next square.
The card covers the central block of squares and pokes into more squares on each of its four sides, giving squares.
This is also the most possible. The card is only inches wide, so its overall width and height are each at most inches; it therefore lies within a block of squares. Its four pointed corners are the only parts that reach the edge of that block, so it can never reach the four corner squares of the block, leaving at most Since is achievable, the maximum is which falls in the range " or more."
Thus, the correct answer is E .
Problem 25 in Other Years
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