Answer:
30.8 inches.
Explanation:
The Pythagorean theorem states that a^2+b^2=c^2, where c is the hypotenuse, or longest side of the triangle opposite to the right angle, and a and b are the two legs of the triangle (the other two sides.)
In the question, we are imagining the TV as a triangle, where its width and height are two sides, and the length diagonally across is the hypotenuse. If its width and height are 25in and18 in, then that would mean that a and b in the equation are 25 and 18. Remember that it doesn't matter which variable you assign (a or b), both are just legs of the triangle.
Plugging 25 and 18 into the equation, we will get that 25^2+18^2=c^2, with c being the diagonal size of Isaac's TV. 25 x 25 = 625 and 18 x 18 = 324, so 625 + 324 = c^2, or, c^2 = 949.
However, this is still c^2, not c, so we must take the square root of both sides. This is because the equation is now essentially saying that c x c = 949, so if we find a number that when multiplied by itself equals 949, that number will be c. to do this, we must take the square root of 949. This will give us an irrational number- approximately 30.8058436. The question asks to round it to the nearest tenth though, so this will simply become 30.8.
In the context of this question, it means that Isaac's television is 30.8 inches long diagonally.