2 players
Draw a tic tac toe board.  One person will be odd numbers (1, 3, 5, 7, 9) and blue chalk, the other person will be even numbers (2, 4, 6, 8, 10) and red chalk.

The first person starts by marking one of their numbers in one of the nine squares.  The next person marks one of their numbers in a different square – much the way you fill in x`s and o`s in tic tac toe. 
The goal of this game is to get a line in any direction – up, across or horizontal, that adds up to 15.  Once you add a number to make a scoring line, mark it thru with your coloured chalk.   Keep playing (make new tic tac toe boards as necessary) until one of the players gets 10 scoring lines & is the winner.

tic tac toe - numbers