Learning Management Using 5 Steps Learning Process for Improving Geometric Reasoning Ability of Matthayom Suksa 3 Students.

The purpose of this research was to study the geometric reasoning ability of Matthayom Suksa 3
students after receiving learning management using 5 steps learning process on reasoning about triangles
compared with 70 percent criterion. The sample group consisted of 30 Matthayom Suksa 3 students in
the first semester of the academic year 2021 of Matthayom Wat Nongkhaem School. They were selected
by purposive sampling. The research instruments were 7 lesson plans using the 5 steps learning process
on reasoning about triangles and geometric reasoning ability test on reasoning about triangles. The
research result found that the geometric reasoning ability on reasoning about triangles of the students
after learning by using the 5 steps learning process had an average score of 20.43, representing 68.10
percent of the total score, which was a little lower than the 70 percent criterion.