Exercise - Focal length and angle of view

Using my kit lens and telephoto lens, I took 3 photos of my bookcase with 3 different focal lenth, 18mm, 55mm (standard)and 250mm respectively.
Having all 3 photos printed on A4 paper and standing where I was, the following was noted:

a) with 55mm standard focal length, to make the objects on the photo appear the same as in real life, I held the paper at 61cm from my eyes.







b) with 18mm wide angle focal length, I had to move the A4 size photo closer to my eyes to the distance of 24cm between my eyes and the paper.








c) with 250mm telephoto zoom lense, the A4 size photo was far too big to move beyond the bookcase so I couldn't measure the distance.