# Exercise: Use two variables and the CALCULATE function to create a ratio

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The answer to the exercise will be included and explained if you attend the course listed below!

 Category ==> Power BI Desktop  (26 exercises) Topic ==> Advanced measures  (1 exercise) Level ==> Average difficulty Course ==> Power BI Desktop
Before you can do this exercise, you'll need to download and unzip this file (if you have any problems doing this, click here for help).

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If you haven't already done so, run the SQL script in the above folder to generate the Make-a-Mammal database.

Create a new Power BI Desktop file, and load the tables from this database into your model.  Using variables, create a measure which allows you to show this matrix:

The matrix shows for each cell the ratio between sales for that cell and sales for four- and six-legged animals for the same filter context.

Here's a suggestion of variables to create within your measure:

Variable What it could equal
FourLeggedSales The total value of sales for the current filter context, but for animals with 4 legs
SixLeggedSales The total value of sales for the current filter context, but for animals with 6 legs
ManyLeggedRatio A/B, where A = the total sales for the current filter context, and B = the sum of the previous two variables

Save this workbook as Variable fun, then close down the Power BI instance you're using.