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## #3244. Subtraction Shopping

Mathematics, level: Elementary
Posted Mon Oct 11 11:20:58 PDT 2004 by Danielle Mattiuz (daniellemattiuz@yahoo.com).
University of Pittsburgh at Johnstown, Johnstown, PA, USA
Materials Required: Unifix Cubes, Base ten blocks, overhead projector and overhead projector papers, markers, paper
Activity Time: 15 minutes
Concepts Taught: Two digit subtraction

Academic Standards: 2.1 Numbers, Number Systems and Number Relationships. 2.1.3 A. Count using whole numbers (to 10,000) and by 2's, 3's, 5's, 10's, 25's and 100's. B. Use whole numbers and fractions to represent quantities. L. Demonstrate knowledge of basic facts in four basic operations. 2.2 Computation and Estimation. 2.2.3 A. Apply addition and subtraction to everyday situations using concrete objects. B. Solve single- and double-digit addition and subtraction problems with regrouping in vertical form. 2.5 Mathematical Problem Solving and Communication. 2.5.3 A. Use appropriate problem-solving strategies. C. Select and use an appropriate method, materials and strategy to solve problems, including mental mathematics, paper and pencil and concrete objects.

Objectives:
 Students will be able to subtract two digit numbers.
 Students will be able to check each other's answers for accuracy.

Materials: Unifix Cubes, Base ten blocks, overhead projector and overhead projector papers, markers, paper, colored paper.

Vocabulary: Initials

Instructional Procedures:
 Anticipatory Set: I will be doing a review of two-digit subtraction to prepare for the activity today. Say to the students, "Today we're going to be reviewing our two-digit subtraction today and then we'll be doing a fun activity. First, let's review." Review two-digit subtraction with the students on the overhead. Give examples without borrowing first and then add in a few with borrowing. Ask some students to come up to the front of the classroom to help.

 Closure: Ask the students to remove the paper from the object that they hung up, not anyone else's, just their own and bring it back to their seats. Ask them if they had a hard time with this or if it was easy. Ask them how they decided to go about choosing items and why they chose the items that they did. I will continue with this conversation until the students have said all that they wanted to about the topic or until we run out of time.

Assessment:
 Assess the accuracy of students' work.
 Assess the students' ability to work in groups.

Special Needs Adaptations: A student with ADHD is in my classroom with an aid. He is usually well-behaved with the aid near, so I will place him in a group with a well-mannered child and he should be fine. If he acts up the aid takes care of him. If he becomes too disruptive I will remove him from his group.

Extension/Enrichment: I could give the students a page in their workbooks to do for homework if I see that they are having difficulty with the subtraction.

Technology Integration:
 One computer: I will use the computer at the beginning of the classroom on a power point presentation. It will include 6 slides each describing a different step in the activity which we will be doing. For example one slide will depict a math problem of \$99 - \$10 with the answer not shown. The last slide is a complete list of rules that the students can refer to at any point during the exercise.
 Six computers: When the children finish the activity they will be allowed to go to the computers in the back and play baseball on http://www.funbrain.com/math/index.html. They must choose subtraction and in the box labeled "difficulty" they are to choose medium. They may move on to hard if they are doing the problems with little to no difficulty.
 One computer for each child: Students will either use a calculator available to them on their computer or on this website: http://www.myschoolonline.com/page/0,1871,21904-175851-24-14522,00.html. They will type in 99 and subtract all of their shopping amounts using this calculator. It should be similar to 99-11=88, 88-5=83, 83-10=73, and so on. This will be used for self correction on the students' behalf.