I Am Full Of Useless Knowledge
The boy was confused about significant numbers so we watched a youtube video about it. I remember in those days I was just as confused, but with no recourse, I had to try many many exercises to see if I finally grasped those rules.
Sad to say - now I have forgotten what I have learnt.
Until today, those significant number rules do not seem very significant to me. Neither have I ever used trigonometry or logarithms after that. Those hours and days spent poring over Maths ten-year series seem like exercises in vain. I enjoyed doing them and getting the answers right but really, do they have any practical use in our daily lives? I regret not reading more books then.