How to execute arithmetic operations between Model fields in django

Prologue:

This is a question arising often in SO:

• Subtracting two annotated columns
• Django query with simple arithmetic among model fields and comparison with field from another model
• Django Aggregation: Summation of Multiplication of two fields

And can also be applied here:

• Django F expression on datetime objects

I have composed an example on SO Documentation but since the Documentation will get shut down on August 8, 2017, I will follow the suggestion of this widely upvoted and discussed meta answer and transform my example to a self-answered post.

Of course, I would be more than happy to see any different approach as well!!

Question:

Assume the following model:

class MyModel(models.Model):
    number_1 = models.IntegerField()
    number_2 = models.IntegerField()
    date_1 = models.DateTimeField()
    date_2 = models.DateTimeField()

How can I execute arithmetic operations between fields of this model?

For example, how can I find:

• The product of number_1 and number_2 of a MyModel object?
• How to filter items where date_2 is 10 or more days older than date_1?