Sometimes you can prove an answer is correct by trying many examples.

Libby thinks that adding
2 odd numbers will always
give an answer that is an
even number. 

odd  +  odd  =  even
 

Libby's examples proved to her that she was
correct in thinking:
odd  +  odd  =  even

Then Libby wondered if this worked the same with multiplying. 
So she decided to try multiplying 2 odd numbers to see if the product was even.
 

    Libby's examples proved to her that :
odd  x  odd  =  odd
 

    Trying many examples can help you to understand a problem.