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Flexibility wanted with variables

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Feature idea (LEVEL 2)
Jeremy Walker

It would be great if variables could refer to other variables.

For example, Kevin McBride contacted me with this particular problem.

He wanted to set up a problem where students were given a number and told that it was a certain fraction of a whole.  They were then to calculate the whole.

In other words:

If x is y/z of the whole, then what is the whole?

Answer=x/y*z. 

If 15 is 3/4, what is the whole?

Answer= 20

Here's the catch, he wants the x variable to be a multiple of the y variable.  He would also like the z variable to always be greater than the y variable but less than 14.

His solution so far has been to create a separate problem for each y.  Here's a few examples:

Type: F
Options: Number
Score: 2, Partial, Round
Groups: WhatIsWhole
Var: x = 3,6,9,12,15,18,21,24,27,30,33,36
Var: y = 3
Var: z = 4..13
7) If $x$ is `$ \small \frac{$y$}{$z$} $` of the whole, what is the whole?
_____
@ The correct answer is $eval($x$/$y$*$z$,#)
a. $x$/$y$*$z$
//What is whole? Numerator is 3

Type: F
Options: Number
Score: 2, Partial, Round
Groups: WhatIsWhole
Var: x = 4,8,12,16,20,24,28,32,36,40,44,48
Var: y = 4
Var: z = 5..13
8) If $x$ is `$ \small \frac{$y$}{$z$} $` of the whole , what is the whole?
_____
@ The correct answer is $eval($x$/$y$*$z$,#)
a. $x$/$y$*$z$
//What is whole? Numerator is 4

So, what we would really like to see is something like this:

Type: F
Options: Number
Score: 2, Partial, Round
Groups: WhatIsWhole

Var: w = 1..12

Var: y = 3..12

Var: x = $y$*$w$

Var: z = ($y$+1)..13

8) If $x$ is `$ \small \frac{$y$}{$z$} $` of the whole , what is the whole?
_____
@ The correct answer is $eval($x$/$y$*$z$,#)
a. $x$/$y$*$z$
//What is whole? Given is multiple of numerator up to 12; numerator bounded by 3 and 12; denominator larger than numerator, bounded by 13

Does that make sense?

Please let me know what questions you have.

Thanks!

 

Comments (1)

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Flew Flewelling

This is one of my top three requests for variables!

  1. Allow the ability to define a variable from another variable.
  2. Allow the ability to define student input as a variable.
  3. Have a global variable for an assignment (Currently variables are either course or question, nothing in between.)
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