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Ella's computer monitor has a 20-inch screen, which means that the length of the diagonal
of the screen is 20 inches. There is a 1-inch margin along the four sides of the screen.
The monitor can be laid flat so that it just fits into a box that is 11 inches wide.
How long is the box?
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From the problem, we conclude that one of the two dimensions of the screen is
11 - 1 - 1 = 9 inches.
Hence, applying the Pythagoras, we find that the other dimension of the screen is = = 17.86 inches (rounded).
It tells us that the corresponding dimension of the box is 17.86 + 1 + 1 = 19.86 inches.
Since this dimension is greater than 11 inches, we have every reason to call this dimension
as "the length of the box".
ANSWER. The length of the box is 19.86 inches.
Solved.