I'm admittedly pretty bad at basic speed math (even dividing by 5 takes me a bit -- and I know it shouldn't). I use the same fibonacci trick, and at least for m

I'm admittedly pretty bad at basic speed math (even dividing by 5 takes me a bit -- and I know it shouldn't). I use the same fibonacci trick, and at least for me it really is much easier. It's important to remember that all arithemtic tricks are made more useful when combined with others. I don't know what fibonacci number is close to 500, but I don't need to: 5 -> 8 means 500 -> 800. Really, the only fibonaccis I have memorized are 2,3,5,8,13,21. 150 is harder, but I would use the same trick. 13->21, so 150->230 plus a bit. Maybe 240.