Thread: scale?

I need help with some math.


I need to turn 4 to 20 into a scale of 0 to 5


example:


I need math to turn this:

4 = 0 pounds

12 = 500 pounds

20 = 1000 pounds


into this:
0 = 0 pounds

2.5 = 500 pounds

5 = 1000 pounds


so it is scaled.

can it be done?

$\displaystyle x\mapsto \frac5{16}(x-4)$?

could you explain your formula a little

First I shifted the back by 4, so that the interval 4 to 20 becomes the interval 0 to 16. Then I scaled by 5/16 so that the interval 0 to 16 becomes the interval 0 to 5. Is that what you want?

first of all, thanks for your help!

I am not sure. I will do some checking and get back to you.

Originally Posted by maddas

First I shifted the back by 4, so that the interval 4 to 20 becomes the interval 0 to 16. Then I scaled by 5/16 so that the interval 0 to 16 becomes the interval 0 to 5. Is that what you want?

lets say that i have 2 scroll bars, the one on the left scrolls between
4 & 20 with 1/10 increments. when I scroll this scroll bar to 12 the scroll bar on the right displays 2.5


so, if the left scroll bar was set to 1.1, what would the scroll bar on the right show??


I hope this explains it better.

If the left scroll bar scrolls between 4 and 20 how can it be set to 1.1? The formula I gave works for 12 ($\displaystyle \frac5{16}(12-4) = 5/2 = 2.5$)...

Originally Posted by maddas

If the left scroll bar scrolls between 4 and 20 how can it be set to 1.1? The formula I gave works for 12 ($\displaystyle \frac5{16}(12-4) = 5/2 = 2.5$)...

sorry, i should have said: 5.1 for the left scroll bar.

Originally Posted by maddas

If the left scroll bar scrolls between 4 and 20 how can it be set to 1.1? The formula I gave works for 12 ($\displaystyle \frac5{16}(12-4) = 5/2 = 2.5$)...

sorry, I am at a loss to understand your answer

Sorry. Suppose the left scroll bar is at position x. Then I think the right scroll bar will be at position $\displaystyle \frac5{16}(x-4)$.

does your formula mean:


5/16 TIMES (x-4)

Yes, what did you think it meant?

I just wanted to make sure.

how do I turn 15/16 into a decimal?