Obvious? It's subjective.

In English class, we are asked to be "clear" in our writings. This means that we should always explain what we say, and make sure that any reader can easily understand our pieces of writing. This is a reasonable expectation because without clarity, a piece of writing will be harder to understand and therefore less effective. However, how can we define "clear?" Doesn't the word "clear" have a different definition for everyone? Isn't it a subjective thing that all depends on each person's understanding or interpretation of the subject?

Consider these two sentences:
"Joe seems happy because he smiles everyday" and "Joe seems happy because he reads everyday." The former should make a lot more sense than the latter because smiling is an action that we usually associate with happiness, whereas reading is not. Therefore, since there is not an obvious link between reading and happiness, the second sentence is unclear if there is no mention of the fact that Joe enjoys reading.

Here is the problem: the last two sentences you just read are all based on our understanding, or rather, my understanding about happiness. If my understanding is different from yours, then those two sentences would not have been clear to you at all. And this is often the case—people's understandings are not always the same, and if the writer makes a wrong judgement of the reader's understanding of the subject, their piece of writing is either going to not have enough explanations, or to be filled with meticulous details. Personally I find this very hard to grasp, as things are not always black-and white, and there is seldom a clear boundary between things.

I face the same problem in math class, except I find it even harder cope with. For example, once in a math test I was given the radius and height of a cylinder and was asked to calculate its new height after the volume has been multiplied by 1.1 (the radius stays the same). To me it was obvious that for a cylinder, as long as the radius was constant, the proportion of the height to the volume would also be constant.  Therefore I simply multiplied the original height by 1.1 and obtained the answer. Guessed what happened? I got a few marks off because I never calculated the volume of the cylinder. 

Also, once in elementary school I got 8% off of a math exam for doing some simple arithmetic in my head and not showing my work (which the teacher never specified to do). In both instances, I got marks off because something was obvious for me when it was not supposed to be–me and my teacher's interpretations of "hard" were different . And how can I possibly know what is and what is not "supposed" to be obvious for me when these standards are all set up by teachers? As a result, I either not show enough work and get marks off, or show too much work and not finish the test, quiz or exam in time.

I simply started writing about this topic because this is a problem that I have been struggling with since I was little, and it is increasingly bothering me. Now that every mark and every percent matters, I really hope that I can get used to what the teachers expect.