If we multiply 0.8 by 1/50, we get 0.8 × 1/50 = 0.8/50 = 0.016 meter. So, we can say 0.016 meter wide should the door be on the scale drawing, if the ratio is 1 to 50.

the ratio is 1:50

this means that 1 meter in the drawing is equal to 50 meters in real life, but that is a complicated way of stating something simple since drawings are not generally measured in meters.

the door is 0.8 meters wide or 80 centimeters wide

in our drawing, the door should be 80 / 50 = 1.6 centimeters wide

the whole purpose of a scale is to allow us to work with smaller units, that is why we have to work with them. It is true that 0.016 meters = 1.6 centimeters, but as I said before, writing the answer in meters just complicates things and makes them harder to understand. You could also say it is 0.000016 kilometers wide and it would be right, but too confusing.

25% is the answer

96 cm is the answer.