PS/IS 686 | Brooklyn, NY

Grade 1, Math, Double Decker Bus

Hello Families,

The first grade classes are starting a math investigation called “Double Decker Buses.” In this real-world context, the children will explore the amounts of people on a double decker bus. Some passengers will sit on the top, and some will sit on the bottom.

In this unit, your child will be using a manipulative called an arithmetic rack, also called a “rekenrek.” This is our model and tool to act out the story. The rack is a calculating frame consisting of two rows of ten beads – two sets of five (one set of red beads, one set of white beads) per row.

Here is what the rekenrek looks like…


In this unit, children move the beads on the rekenrek to represent passengers going from one deck on the bus to the other. They will model passengers sitting in different combinations of the red and white seats.

This context will support your child in learning:

  • different strategies for adding single-digit numbers
  • the relationship between addition and subtraction
  • the commutative property of addition (5+4 = 4+5)
  • the idea of equivalence (numbers can be named in many ways)
    • Ex: 10 equals 5+5, 6+4, 2+8, 5+3+2, etc.

We are looking forward to really getting into this unit with our students!

Thank you!

First Grade Teachers