Teaching High School Age Students with Special Needs the Four Situations for Subtraction

All learners, including those who qualify for special education services, should have access to learning mathematical concepts. This study examined the efficacy of using hands-on sets of materials to teach two high school students with mental retardation the four situations for subtraction. This is a mixed methods study using a simple pretest-posttest design to determine correct interpretation of subtraction story problems for different situations (take-away, comparison, completion, and whole-part-part) and correct regrouping during dynamic subtraction. Eight story problems were presented to the two participants eight weeks prior to instruction; students answered an identical posttest after twelve half-hour lessons on subtraction story problems and regrouping, which occurred during a two-and-a-half week period. Qualitative teacher observations of the two students were used to triangulate the data. On the pretest, students scored poorly, with one student completing none of the eight items correctly and the other completing three. The non-take-away subtraction situations confused the students and they made many regrouping errors during dynamic subtraction. On the posttest, both students solved all the problems correctly. Teacher observations indicated that students found the hands-on materials engaging and motivating, using the manipulatives to help them during regrouping. The materials and method of teaching were effective for the following reasons: the sets of objects suited the concrete developmental stage of the students; a variety of colorful and exciting materials were used to pique and sustain student interest; the teacher modeled and verbally explained how to solve the problems using the hands-on materials; the teacher encouraged interaction and elicited students explanations; and students were moved from the concrete manipulatives to the more abstract nature of word problems. The authors recommend that these materials not only be used with primary grade students to teach subtraction situations, but with other students with special needs (19 references; 2 tables, one containing photographs of materials and the other showing the pretest/posttest questions)