Head or Calculator?
For estimation questions at interviews (like Google) do you get to use a basic calculator (on your phone) or do you have to just do it all by head?
Google Eggman Jul 4, 2018
Phone, super quick
Google bch Jul 7, 2018
Nope. If you can't do simple math with clever rounding, I don't think PM is the right path honestly.
Google downlevel? Jul 4, 2018
Head. Use easy numbers (multiples of 5 or 10)
Do it in your head. Feel free to approximate/round up or down where convenient. It is an estimation after all, so you don't need to get the right answer to the fourteenth decimal place. If you are not wrong by an order of magnitude, you should be fine.