>> Day 8 it is 10.
I did it a little differently.
Tree doubles every day, so it *halves* every “yesterday”. Today (day 10) it’s 40 feet.
So yesterday (day 9) it was half that — 20 feet.
Day before that (day 8) it was half THAT — 10 feet. Done.
Not that there’s anything wrong with logarithmic math.
Sometimes test taking requires quicker stragegies though.
Your solution is great! But what if they were a little sneakier and asked you how much time would elapse before the tree was 16 feet? ;)
I’d also be better off not converting it to decimals.