scale?

**RonR399** · Apr 12th 2010, 01:21 PM

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?

**maddas** · Apr 12th 2010, 01:30 PM

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

**RonR399** · Apr 12th 2010, 01:32 PM

could you explain your formula a little

**maddas** · Apr 12th 2010, 01:34 PM

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?

**RonR399** · Apr 12th 2010, 01:35 PM

first of all, thanks for your help!

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

**RonR399** · Apr 12th 2010, 01:40 PM

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.

**maddas** · Apr 12th 2010, 01:59 PM

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 ( $\frac5{16}(12-4) = 5/2 = 2.5$ )...

**RonR399** · Apr 12th 2010, 02:06 PM

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 ( $\frac5{16}(12-4) = 5/2 = 2.5$ )...

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

**RonR399** · Apr 12th 2010, 02:10 PM

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 ( $\frac5{16}(12-4) = 5/2 = 2.5$ )...

sorry, I am at a loss to understand your answer

**maddas** · Apr 12th 2010, 02:16 PM

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

**RonR399** · Apr 13th 2010, 01:28 PM

does your formula mean:

5/16 TIMES (x-4)

**maddas** · Apr 13th 2010, 06:36 PM

Yes, what did you think it meant?

**RonR399** · Apr 14th 2010, 01:08 PM

I just wanted to make sure.

**RonR399** · Apr 17th 2010, 04:30 AM

how do I turn 15/16 into a decimal?

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