teaching math
posted by barbara .
Indicate whether the deductive reasoning used is an example of affirming the hypothesis or denying the conclusion.
If a number is divisible by 3, then the sum of the digits of that number is divisible by 3.
The sum of the digits of a number is not divisible by 3. Therefore the number is not divisible by 3.

The fallacy of affirming the hypothesis is based on the following hypothesis:conclusion set
If A then B, IF B then A.
The fallacy of denying the conclusion is
If A, then B; If NOT B, then NOT A
Does that help? 
If you are teaching Math, the way to teach these is to demonstrate with Venn Diagrams, in my opinion. STudents understand spacial arguments better than written logic.