The size of a flat-screen television is given as the length of the screen’s diagonal. How many square inches greater is the screen of a square 21-inch flat-screen television than a square 19 -inch flat-screen television?
Choose the correct choice from the following
A) 42
B) 40
C) 38
D) 36
E) 48
If we take a square with side length x and draw a diagonal, we get two isosceles right triangles.   If we focus on one such right triangle, we see that the legs have length x.   square 21-inch flat-screen television   The diagonal (hypotenuse) = 21   So, we can apply the Pythagorean Theorem to get x² + x² = 21²   Simplify: 2x² = 21²   Divide both sides by 2 to get: x² = 21²/2   Since the area of the square = x², we can see that the area of this square is 21²/2   square 19-inch flat-screen television   The diagonal (hypotenuse) = 19   So, we can apply the Pythagorean Theorem to get x² + x² = 19²   Simplify: 2x² = 19²   Divide both sides by 2 to get: x² = 19²/2   Since the area of the square = x², we can see that the area of this square is 19²/2   DIFFERENCE IN AREAS =21²/2-19²/2   = (21+19)(21-19)/2 =40   40
<result>B</result>
The size of a flat-screen television is given as the length of the screen’s diagonal. How many square inches greater is the screen of a square 21-inch flat-screen television than a square 19 -inch flat-screen television?