Web-based Practice
Color Chips - Subtraction by NLVM
Subject
Math, Science & Technology
Virtual Manipulative
Click here for this interactive resource.
Description
This manipulative is designed to help conceptualize the combination of signed numbers (positive and negative integers). A key idea is that a black chip (representing 1) and a red chip (representing -1) together add to 0. At the point where chips are to be combined, dragging a black and a red chip together (placing one on top of the other) makes the pair disappear (visually emphasizing that the sum is 0).
For each new problem the user is prompted to drag chips into the workspace to represent the difference. Thus, for the difference 5 - (-3) we would drag in five black chips. Then the user is and asked to drag in three joint red and black chips. The user is then asked to take away the red chips. Finally the user is asked the difference. If the chips do not represent the value at a particular stage, the user is asked to try again until the chips in the workspace do match the correct value.
When students first encounter negative numbers, it is certainly helpful to talk about examples of positive and negative numbers that match their experience, as in almost any process that can go in two directions (temperature, receiving and giving ("owing") small amounts of money, moving along a number line, etc.), from which the observation of combining 1 and -1 to get 0 has meaning. Relating this virtual manipulative to some sort of physical or experiential example will make its work and conclusions much more sensible.
Content Provider
The National Library of Virtual Manipulatives is a three-year NSF supported project to develop a library of uniquely interactive, web-based virtual manipulatives or concept tutorials, mostly in the form of Java applets, for mathematics instruction (K-8 emphasis). The project includes dissemination and extensive internal and external evaluation. For more information, please visit http://nlvm.usu.edu/en/nav/vlibrary.html.
Credits
Principal Investigators
Larry Cannon
Jim Dorward
Bob Heal
Leo Edwards
Java Applet Programming
Ethy Cannon
Joel Duffin
David Stowell
Zeke Susman
Richard Wellman
Jennifer Youngberg
Web Site Programming
Joel Duffin
