Strike it Out
This is a game for two players.
Start by drawing a number line from $0$ to $20$ like this:
The first player chooses a number on the line and crosses it
out.
The same player then chooses a second number and crosses that out
too.
Finally, he or she circles the sum or difference of the two numbers
and writes down the calculation.
For example, the first player's go could look like this:
The second player must start by crossing off the number that player
$1$ has just circled.
He or she then chooses another number to cross out and then circles
a third number which is the sum or difference of the two
crossed-off numbers.
Player $2$ also writes down their calculation.
For example, once the second player has had a turn, the game could
look like this:
Play continues in this way with each player starting with the
number that has just been circled.
For example, player one could then have a turn which left the game
looking like this:
The winner of the game is the player who stops their opponent from
being able to go.
This PowerPoint
presentation also demonstrates how to play the game.
You may like to click through it.
Now it's your turn!
Try playing the game a few times to get a feel for it.
What is your strategy for winning?