Introduction
Dr. Word Problem and the Four Operations is a unit focused on the four operations of arithmetic. This unit explores the use of Singapore bar models as a tool for solving word problems. The unit teaches students how to represent word problems with Singapore bar models beginning with a basic addition fact. The lessons are scaffold to help the students to understand how to draw models to represent subtraction, multiplication, and division. The final phase addresses representing multi-step problems with bar models.
While the students at my school are high achievers in mathematics, word problems seem to be the weakest area of the math curriculum for them. My fourth graders typically have a difficult time deciding which operation a word problem requires. Often I find my students using some of the coping strategies and limited strategies that Sowder (1995) describes. One coping strategy that they use is adding the numbers that they find in the problem, regardless of what the word problem states. Another poor strategy choice is "Limited strategy 5, looking for isolated key words to tell which operation to use". This strategy is taught over and over at each grade level. Since each word problem is slightly different, children cannot figure out a strategy that automatically works for each one. Therefore, students try to develop coping strategies. Some teachers on the other hand are either teaching some of these limited strategies that are described in their teacher's manual, or they are teaching their students the way they were taught in school. This unit tries to look at word problems in a different way, so that students can develop a greater mathematical understanding that will enable them to be more successful problem solvers.
Through my work on this project, after analyzing word problems and looking for similarities and differences I have come to the following conclusions. When working with the simpler problems, students can learn and become more familiar with the basic structure of word problems. However, beyond the basic structure students will encounter differences within each problem. The subtle differences among very similar problems further complicate this subject matter. As students deal with multi-step problems there definitely is not a set approach to take. The students must truly understand what is going on mathematically in each situation.
So in this unit I have examined problems and grouped them into suites. The words and situations are different within the suites, but the basic structure is the same. By examining the different dimensions of the suites of problems, I have learned to approach problem solving in a clearer, more systematic way than I did in the past. This unit not only looks at the suites of problems, but also introduces the students to the Singapore bar models as a strategy for solving word problems.
The Singapore bar models provide the students with a visual component to help them understand what is going on mathematically in the problem. These models can be used to represent the four operations pictorially. The Singapore bar models are easy to draw and can be used to solve algebra problems without writing an equation. Hopefully, the combination of bar models and analyzing suites of problems will lead students and teachers to more successful problem solving and help to avoid some of the pitfalls caused by coping and limited strategies.
Attaching symbolic meaning to words is a difficult task for students at all levels. In fourth grade the students have just learned the four operations. This is really the first time that they have four operations to choose from when solving a problem. Their level of understanding the operations of multiplication and division, in particular, is in the beginning stages. So, word problems further complicate the issue because they have to figure out the words, the operation needed, and then they have to attach symbols to the words. This unit is intended to help students learn which mathematical operations to use when certain actions are presented in a problem. Upon completion of the unit I expect the students will have developed a greater understanding of the concepts of all four operations, and especially multiplication and division.
This unit is designed to be taught over a three-week period for approximately forty-five minutes per lesson. Beginning with addition, the students will experience suites of addition problems and the related subtraction problems. Next, the unit will move into multiplication and the related division problems. At the start, the suite of problems will involve one diagram focused around one scenario. These problems will have the same story line, but will be slightly different. The students will later face individual problems, not connected to their related counterparts, and the problems will involve one of the four operations. This is a more typical representation of the real world, where a word problem stands alone. After the students have learned the four operations and how to represent problems from all of the operations using a Singapore bar model, they will study two-step problems involving the four operations in any combination. The culminating activity will be for the students to put together a collection of word problems that include all four operations focused around a theme. My students will write their own word problems around one scenario of their choice, and also illustrate their scenarios with Singapore bar models.
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