Bunk Beds and Apple Boxes: Early Number Senseis one of eight units in the Contexts for Learning Mathematics' Investigating Number Sense, Addition, and Subtraction (K-3) This unit begins with the story of a pajama party-a sleepover during which eight children play, moving up and down bunk beds, teasing the babysitter who imagines she is losing and then gaining children The unit introduces the arithmetic rack as a powerful model...