I was reviewing percentages with my son (US equivalent of 7th grade) and the more I dug into explanations, the less I could understand why they are taught.
I understand how they technically work but using them introduces, I think, a complexity layer which does not help in the actual computation.
Some subjective thoughts:
- $20\,\%$ is $0.2$ of something. In order to get $20\,\%$ of $123\,€$, I need to first realize that $20\,\% = 0.2$, and then compute $123·0.2$. So the existence of a percentage did not help in the calculation.
- the fact that $20\,\%$ seems easier to grasp than $0.2$ is, I believe, just a matter of being used to it. After some time $0.2$ would seem natural as well.
- percentages being on a scale of $0\,\%$ to $100\%$, things like $130\,\%$ may seem weird. $1.3$ is better, it shows that there is one whole, and then $0.3$.
Is there a specific reason percentages are a thing?