Answer: 20 feet
Step-by-step explanation: To find the diagonal distance from one corner to the opposite corner of Bernard's rectangular bedroom, we can use the Pythagorean theorem, which states that the square of the length of the hypotenuse (diagonal) of a right triangle is equal to the sum of the squares of the lengths of the other two sides.
In this case, the two other sides are the length and the width of the room, so we have:
diagonal^2 = 12^2 + 16^2
diagonal^2 = 144 + 256
diagonal^2 = 400
Taking the square root of both sides, we get:
diagonal = √400
diagonal = 20 feet
Therefore, the diagonal distance from one corner to the opposite corner of Bernard's rectangular bedroom is 20 feet.