AmberCutie said:
Because people are still confused i think, I will retype what Luna said with one change. The = is throwing people off.
4560 tokens / 20
Is the same as
456 / 2
But the latter feels easier to do in your head. So models like a total that ends in 0 so that they can do easier math in their head vs. dividing by 20.
I actually multiply by .05 instead of dividing.
Another way of thinking about it is the way we were taught in elementary school. Factors. 20 has the factors of 1 and 20, 2 and 10, 4 and 5 in pairs. So anytime you wish to divide a number by 20 you can INSTEAD divide that number by the factors of 20 and get the same result.
So dividing 456 by 20 gives 22.8
OR dividing 456 by 5 then dividing that new number by 4 still gives the same 22.8
and dividing 456 by 10 then dividing that number by 2 gives the same 22.8
It doesn't matter if you use the original number or any of the proper factors of the number.
So in dealing with tokens it makes the most sense to use the factors 10 and 2 because 10 is the easiest to divide any number by, simply move the decimal place one to the left. The divide that new number by 2. This can easily be done in our heads.
<<<<<< TRIGGER WARNING - MATH GEEK EXPOSITORY FOLLOWS!!! >>>>>>
To expand this even further you can easily figure out any percentage quickly in your head to pay tax for items or tips at restaurants.
You simply have to remember that 10% means moving the decimal to the left one place and 1% moves it two places to the left. And you have to understand that the little percentages can be figured individually then added up to get the right answer. So 7% is the same as 5% plus 2%. Or 8% is the same as 10% minus 2% and so on. (advanced would be 1.5% is the same as 1% plus one half of 1%)
For example if you want to figure out 5% of some number you can figure out the 10% and then divide that number in half.
For 3% figure out the 1% and times that number by 3.
For 7% do the 10% and divide in half but also figure out the 1% and double that. Add those two together and you have 7%
After you get comfortable with that you can expand it further by doing 1% and dividing that in half for 0.5%. Divide that number in half for 0.25%. You can really carry it out easily as far as you want. So in city's that charge an odd tax on items you can calculate 7.85% in your head with no problem.
Next time your in the grocery store try just figuring out the tax on an item in your head for practice. It gets easier the more you do it.