To find the width of Fiona's TV screen, we can use the Pythagorean theorem. The TV screen forms a right triangle where the length and width are the two legs, and the diagonal is the hypotenuse.
Let:
- \( L = \) length of the TV screen = 20 inches
- \( W = \) width of the TV screen (unknown)
- \( D = \) diagonal of the TV screen = 25 inches
According to the Pythagorean theorem:
\[ D^2 = L^2 + W^2 \]
Plugging in the known values:
\[ 25^2 = 20^2 + W^2 \]
Calculating the squares:
\[ 625 = 400 + W^2 \]
Now, isolate \( W^2 \):
\[ W^2 = 625 - 400 \] \[ W^2 = 225 \]
Taking the square root of both sides:
\[ W = \sqrt{225} \] \[ W = 15 \]
Thus, the width of Fiona's TV screen is 15 inches.