Answer: Door 2 will fit through the rectangular door.
To do this problem, we need to use the Pythagorean Theorem. The door is a rectangle and if we draw a line from corner to corner, we have right triangles.
To find the diagonal distance, we have to write and solve the equation below.
3^2 + 9^2 = c^2
9 + 81 = c^2
90 = c^2
c = the square root of 90
The square root of 90 can be simplified to 3 square roots of 10.