Topic: Odd and Even

Odd and even are the basic property of integer numbers. Although a very simple concept, it can be quite useful to solve some interesting problems.

What we learned:

• different combinations of odd and even number operations:
• odd + odd = even
• odd + even = odd
• ... ... (try to list all the combinations as a review of the class)
• use logic thinking to find out if the result should be an odd or even number

Homework

1. In the class, we learned that we get an even number when adding two odd numbers together. What will we get when we add (any) odd number of odd numbers together? What if we add (any) even number of odd numbers together?



2. On a table, there are 4 coins in a row, one next to the other. All of them have head side up. Can we make all of them tail side up, if we use the rules below? If yes, show how you do it.

• Rule #1: Every time 3 coins must be flipped together. Note, you can pick any 3 coins, i.e. they don't have to be next to each other.
• Rule #2: You can repeat this operation (flip any 3 coins together) as many time as you like