# Mathematical Operations with Multiple Dials

Sep 26, 2017

I am trying to set up multiple dials that interact with one another in a mathematical formula. Specifically, I have four dials, let's call them A, B, C, and D. I'd like to show that A - B - C = D. I'd like the value of D to change when a learner turns either A, B, or C. Essentially, I'd like to set it up such that for every step that A is turned to the right, D is increased by 1, and for every step that A is turned to the left, D is decreased by 1. (And similarly for B and C, only in the opposite direction.)

I cannot figure out a way to do this. I have tried setting this up such that every time A is turned, A is added to D. However, unless D is reset to 0 every time, it will add A to the existing value of D. For example:

1. Turn A from 0 to 1 --> D is changed from 0 to 1
2. Turn A from 1 to 2 --> D is changed from 1 to 3 (because it is adding 2 to 1)

I also cannot set it up such that every time A is turned, 1 is added to D, because:

1. Turn A from 0 to 1 --> D is changed from 0 to 1
2. Turn A from 1 to 0 --> D is changed from 1 to 2

I know I can have the learner set their preferred levels of all three dials (A, B, and C) and then click on a button to get the result for D. But I'd really like to allow the learner to see immediate changes in D as soon as just one of A, B, or C is turned.

Can anyone help? Thanks in advance!

###### 2 Replies

I think I answered my own question! (I didn't realize I could reset dial D to zero, and that rearranging the triggers makes a difference!) I'll leave this here in case someone else is looking for the same solution.

For each of the dials A, B, and C, I added four triggers:

1. When the dial is turned, change D to zero.
2. When the dial is turned, add A to D.
3. When the dial is turned, subtract B from D.
4. When the dial is turned, subtract C from D.

If anyone has another method, I'd love to hear it too! Thanks!

Hi Clara and welcome to E-Learning Heroes :)

Glad you were able to get this figured out and thank you for chiming back in with an update and sharing your solution.

Hopefully others with ideas will chime in to share as well.