Interesting addition and subtraction operation
The naughty squirrel hide and seek, and you come the number of number of mushrooms inside the house in the end a number of little squirrels hiding
The course of the game, the little squirrel in the house constantly walked out, therefore, the children not only to remember the number of remaining squirrels inside the house, and also adds and subtracts the squirrel out of the only correct answer to a hiding squirrel the number to be rewarded
Mainly on the children's memory capacity, there are a number of simple computing power