Doubles and Halves
Use chalks to draw circles on the floor in the garden. Write the numbers 1-10 inside the hoops. Throw a bean-bag or teddy into the hoops and double the number that the teddy lands on.
Why not try setting a timer, how many can you get right in 1 minute? If its too easy make the numbers more challenging.
Repeat for halves; write the numbers 2, 4, 6, 8, 10, 12, 14, 16, 18 and 20 inside the hoops. Half the number that the bean-bag/teddy lands on.