What is the importance of scale in reading maps

A map that is drawn to scale/has a scale means that you can measure a distance on the map and it will be the same on the ground according to the scale. 
Said another way, if I know where I am, (or a given starting point), that is on the map, I can find a second point that I want to get to, measure the distance on the map and it will be the same distance on the ground. 
Note that the units of measurement have to be the same. If the map scale is 1:50,000, then one foot on the map is 50,000 feet on the ground. If it's one shoe on the map (I just put the map on the floor, took off my shoe and put it on the map, made a mark on the map at the heel and another at the toe), then on the ground, the distance will be 50,000 shoe lengths.Source(s):

A,) cause a & b are equal & both gives 180°