12/09/20 Math

In a park, 10 dogs are running on the grass, and 1 dog is sleeping under the tree. 9 of the running dogs leave the park.

How many dogs are left in the park?

• 10 + 9 = 19

• 10 - 9 = 1

  1 + 1 = 2

• 9 - 1 = 8

Alejandro had 9 rocks in his yard and 10 rocks in his room. 9 of the rocks in his room are gray rocks, and the rest of the rocks are white.

How many white rocks does Alejandro have?