On 21 Jun 2012 01:36:50 GMT, notbob wrote:

On 2012-06-20, Steve B wrote:

I am pretty good at math, always was. I can do a lot of things in my head.
I love messing with people who can't.

Easy approach to doing percentages in yer head. Stuff like tips,
discounts, etc:

50% off is easy. Divide by two, or one half.

10% is easy. Divide by 10.

Shift the decimal point.

60% is merely one half plus one tenth, in this case, 75 + 15.

65% is halving the 10% and adding it to the pile.

18%? Divide by 10, halve the 10%, Halve the 5%, and add 'em all up.
That's only 17.5%, but close enough to 18% fer a tip.

Think in terms of cutting everything in half, then adding it back up.
Even a senile old geezer like myself still has enough brain cells left
to pull that trick off.

nb