Tell the kids,
“I’ll say a number, you double it.”
Start with easy numbers (4, 8, 13), work up to harder ones (45, 63, 79). Zero and 1/2 are good ones, also.
“I’ll say a number, you double it and add one (or ten or . . .).”
“I’ll say a number, you double it and subtract one" (or however many).
You can also reverse it:
Add one, then double it or subtract one, then double it.
from:
http://washmath.org/files/GamesAndActivities.pdf