After setting up your GradeBook, you can change how each category average is
calculated.

From the GradeBook, click Settings.

Click the Categories tab.

At the top of the Categories
page, select an assignment category.
Assignments in that category are listed.

Under When Calculating Category
Averages, select how you want to average assignment scores for
this category.
Note When the final score is based on points,
category averages are calculated as point totals regardless of what you select.
 Equally
 The point value of each assignment is normalized so each assignment
in the category has equal weight.
 By Point Values
 The unadjusted point value of each assignment is used as its
weight.
For example, the Homework category average is different depending on how
assignments are weighted:
Weighting 
HW1 Score

HW2 Score

HW3 Score

Category Average 
Equally 
6/10 
35/50 
80/100 
$$\left(\frac{6}{10}+\frac{35}{50}+\frac{80}{100}\right)\u0e23\u0e173=\mathrm{70\%}$$ 
By Point Values 
6/10 
35/50 
80/100 
$$\frac{6+35+80}{10+50+100}=\mathrm{75.625\%}$$ 

Click Save.
If you don't want to update your GradeBook calculations now, first clear
Update GradeBook.