Post History
#3: Question closed
by
Peter Taylor
·
2023-03-23T13:58:45Z (over 1 year ago)
#2: Post edited
by
Chgg Clou
·
2023-03-22T00:37:19Z (almost 2 years ago)
- My 9 year old does not grok [DanielWainfleet](https://math.stackexchange.com/users/254665/danielwainfleet)'s [answer](https://math.stackexchange.com/a/2896762). How can we intuit why percent change divides the difference by the original number, NOT the new number?
- >If a changes to b then $\color{red}{a(1+d)=b}$ so $d=(b/a)−1=(b−a)/a$.
- Why $\color{red}{a(1+d)=b}$? Why can't this be $\color{limegreen}{a+d=b}$? Isn't it more straightforward to symbolize change as $\color{limegreen}{d}$, rather than $\color{red}{ad}$ ?
- If I have 2 apples, and buy 3 more, then my new amount of apples $\color{seagreen}{= 2 + 3 = 5}$. NOT $\color{firebrick}{2(1 + 3) = 10}$.
I bookmarked [a similar question](https://math.meta.stackexchange.com/a/34421), but [Math SE deleted it](https://math.meta.stackexchange.com/a/34421).
- My 9 year old does not grok [DanielWainfleet](https://math.stackexchange.com/users/254665/danielwainfleet)'s [answer](https://math.stackexchange.com/a/2896762). How can we intuit why percent change divides the difference by the original number, NOT the new number?
- >If a changes to b then $\color{red}{a(1+d)=b}$ so $d=(b/a)−1=(b−a)/a$.
- Why $\color{red}{a(1+d)=b}$? Why can't this be $\color{limegreen}{a+d=b}$? Isn't it more straightforward to symbolize change as $\color{limegreen}{d}$, rather than $\color{red}{ad}$ ?
- If I have 2 apples, and buy 3 more, then my new amount of apples $\color{seagreen}{= 2 + 3 = 5}$. NOT $\color{firebrick}{2(1 + 3) = 10}$.
- [Math SE deleted](https://math.meta.stackexchange.com/a/34421) [a similar question](https://math.stackexchange.com/a/4337822).
#1: Initial revision
by
Chgg Clou
·
2023-03-22T00:33:33Z (almost 2 years ago)
If a changes to b, then doesn't a + d = b? Why a(1 + d) = b?
My 9 year old does not grok [DanielWainfleet](https://math.stackexchange.com/users/254665/danielwainfleet)'s [answer](https://math.stackexchange.com/a/2896762). How can we intuit why percent change divides the difference by the original number, NOT the new number?
>If a changes to b then $\color{red}{a(1+d)=b}$ so $d=(b/a)−1=(b−a)/a$.
Why $\color{red}{a(1+d)=b}$? Why can't this be $\color{limegreen}{a+d=b}$? Isn't it more straightforward to symbolize change as $\color{limegreen}{d}$, rather than $\color{red}{ad}$ ?
If I have 2 apples, and buy 3 more, then my new amount of apples $\color{seagreen}{= 2 + 3 = 5}$. NOT $\color{firebrick}{2(1 + 3) = 10}$.
I bookmarked [a similar question](https://math.meta.stackexchange.com/a/34421), but [Math SE deleted it](https://math.meta.stackexchange.com/a/34421).