eng Science and Education Publishing American Journal of Educational Research 2327-6150 2023-04-17 11 4 183 190 10.12691/education-11-4-2 EDUCATION20231142 article Gerald C. Bayarcal 1 Denis A. Tan denistan@cmu.edu.ph 1 Science Education Department, Central Mindanao University, University Town, Musuan, Bukidnon, 8710 Philippines One of the instructional approaches that have the potential to help students develop their problem-solving skills is an open-ended approach (OEA). OEA focuses on finding the correct response rather than offering a single solution to a problem at hand. This study investigated the achievement and problem-solving skills in Mathematics of the Grade 8 students in Binuangan National High School through an open-ended approach (OEA). It sought to: identify the levels of achievement in Mathematics of students who were exposed to OEA and those exposed to non-OEA; determine the problem-solving skills of students who were exposed to OEA and those exposed to non-OEA in terms of: (a) self-confidence about solving problems; (b) putting effort in solving problems; and (c) procedure followed to solve problems; compare the levels of achievement in Mathematics of students who were exposed to OEA and those exposed to non-OEA; and find out the difference on problem-solving skills of students who were exposed to OEA and those exposed to non-OEA. The researchers adopted the quasi-experimental research design in the study. The experimental group and the control group's pretest results showed very poor student achievement; however, after exposure to OEA, the experimental group's posttest results showed great student achievement. Compared to OEA and non-OEA, students exposed to OEA demonstrated greater problem-solving skills. Between the pretest and posttest, OEA considerably raised students' achievement levels. Additional findings showed that students exposed to OEA had significantly better problem-solving skills than students exposed to non-OEA. http://pubs.sciepub.com/education/11/4/2/education-11-4-2.pdf achievement problem-solving skills open-ended approach