5 ms·
From the article: "I know a union that got a substantial pay raise because a politician did not understand that adding and then subtracting 20% gets you to anot
by brockf 16y ago
From the article: "I know a union that got a substantial pay raise because a politician did not understand that adding and then subtracting 20% gets you to another result from the one you started."
Wouldn't this be a pay decrease?
x * 1.2 = y
y * 0.8 < x
- deleted 16y ago[deleted]
- dkersten 16y agoTrue. 20% of y is larger than 20% of x (which is what was added to x to obtain y) because y is a larger number. Therefore subtracting 20% of y from y will give you some value smaller than x. Eg: 100 + 20% = 120; 120 - 20% = 96. Not that anyone here needs an explanation :)
- deleted 16y ago[deleted]
- deleted 16y ago[deleted]
- drbaskin 16y agoI don't whether the error you introduced is intentional or not, but 120 * 0.8 = 96, not 106. Another way of thinking about this is that 1.2 * 0.8 = 0.96, so it is a four percent pay cut. (This is true for any situation like this and can be remembered by the difference of two squares formula from your early algebra class -- (1 + r)(1-r) = 1 - r^2, where r is the fraction raise/pay cut.)
- nano81 16y ago120 * 0.8 = 96, not 106
- deleted 16y ago[deleted]
- JustinSeriously 16y agoI've been trying to work this one through. One possible solution, (using a hefty dose of mathematical illiteracy, that looks like one of those word problems that occasionally appears in Marilyn vos Savant's column): base salary: $100 $100 * 1.2 = $120 $120 * (1.2 * .8) = $115.2 ("It's a 20% pay cut from our pay raise, that's why you have to multiply our pay raise with our pay cut.")
- zb 16y agoTechnically he didn't say that it was the pay that was being added and subtracted. Perhaps it could have been something like, say, hours?
- ciupicri 16y agoIf a sum of money (S0) is increased with p percent then decreased with the same percent, the final sum (S2) will be: S2 = S0 * (100+p)/100 * (100-p)/100 A plot[1] of this equation will quickly show that as p increases, S2 decreases. [1] http://www.wolframalpha.com/input/?i=%28100%2Bp%29%2F100+*+%28100-q%29%2F100 http://www.wolframalpha.com/input/?i=%28100%2Bp%29%2F100+*+%...
- rue 16y agoIt would make sense if the amount in question was from a deduction from pay of some sort, tax, union fee deduction etc., rather than the pay itself.