Using Relational Thinking
Part I: Subtraction on a Dynamic Number line

 

Directions: Drag the red dot on each number line to model the equality.  Fill in the box and then check your answers.

Example 1:  67 - 39 = 68 -    Sorry, this page requires a Java-compatible web browser.   Using your own relational thinking, enter two more equations with a distance difference of 28. You may check using the slider, or click on the "check equation" box.   -    =  28    -    =  28

Example 2:    Consider the problem of 133-47.  Move the slider around to find various combinations of numbers that make this difference.  Consider which of your combinations would facilitate mental math or relational thinking.  For example, would it be easier to compute if the difference began with 135 - 49? Sorry, this page requires a Java-compatible web browser.

Example 3:   324 - 278  =  325 -   = - 300  Sorry, this page requires a Java-compatible web browser.