Report Builder 3.0 - Matrix - Create Column with Percentages based on Totals Column

I have created a Matrix in Report Builder 3.0 for a SharePoint list.  It works great.

The matrix includes data grouped by months and grouped by the number of Yes and No answers to a single question.

Now I would like to add a column that calculates the percentage of the total based on the number of Yes answers.

The matrix looks like this:

Question       Yes    No    Total

Jan                5       5       10

Feb                10    10       20

March             15    10       25

I have a added a new column title Percentage and have tried several different expressions and I keep getting errors.

I would like the matrix to look like this:

Question       Yes    No    Total     Percentage

Jan                5       5       10           50%

Feb                10    10       20          50%

March             15    10       25          60%

The percentage is the Number of Yes answers divided by the Total.

I have search online and cannot find the solution for us.  I thought it would be simple but Report Builder is proving not to be so easy to figure out.  I use Excel Pivot tables all the time and can easily create this in Excel.