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1st Grade Task: Cube Trains

This task asks students to determine the number of green cubes used in a cube train that consists of 12 cubes. This problem involves an “add to” situation with an unknown starting quantity.Students must determine the number of cubes in the cube train by finding the number of cubes in an equivalent train. Connecting cubes or other manipulatives should be available for students to model the problem; however, students may choose to model the problem with a drawing. Students may be able to determine the number of cubes with the model and may not choose to write an equation. Students should be guided to represent the situation with both a model and an equation and to connect the two representations with an explanation of how they know the answer is correct. Some students may benefit from modeling Sam’s train on a part‐part‐whole mat.

Standards & Objectives

Learning objectives:

Students will:

Use addition and subtraction within 20 to solve word problems involving situations of adding to, taking from, putting together, taking apart, and comparing, with unknowns in all positions, e.g., by using objects, drawings, and equations with a symbol for the unknown number to represent the problem.
Apply properties of operations as strategies to add and subtract.

Essential and guiding questions:

Which train represents Sam’s train and how do you know?

How many cubes are in each boy’s train and how do you know?

Describe how you found the solution to the equation.

If the number of Sam’s green cubes are the same as Tom’s red cubes, how would that change the number of total cubes that Sam has?

If Tom gives his blue cubes to Sam to add to his train. How many cubes will be in Sam’s train now? What equation could you write to show this?Which train represents Sam’s train and how do you know? How many cubes are in each boy’s train and how do you know? Describe how you found the solution to the equation.

Activity/Task Variations

Blooms taxonomy level:

Applying

Extension suggestions:

Sam and Tom build a new cube train with pink and white cubes. The train has the same number of cubes as the other trains but has 3 less pink cubes than the number of green cubes in Sam’s train. How many pink cubes and how many white cubes are in the new train? If Tom and Sam build a cube train that is twice as long as the red and blue train, how many cubes are in the new train?

Originator:

Tennessee Department of Education