Because your logic is as wrong as your formula
13,6 eV *
if you don't know the formula, you will not be able to solve the next similar problem where your brilliant mind cannot find shortcuts. Also all the later you learn will be based on the base that you already know that formula, so you won't solve them either. Kids just cannot accept that there was million smarter people before them, and they cannot say anyting new on their level.
Maths education isn't about numbers but about how to solve problems so the method is more important than the answer
Yep, one time my teacher said to me, "Hmm, the answer is right but its not my method that you are using. Marks for answer, but nothing for the method that you used".
That was hillariously funny
Use logic to make formula instead of solving this even if you forget you make the formula with logic