This experimental mixed method study examined the effect of memorization of multiplication tables on students' performance in math at the high school level. Students took a diagnostic multiplication test and a comprehensive assessment in various mathematics topics. The study used two methods of testing and similar instruments. In the first, students used memorization, and in the second they used calculators. Also, a questionnaire was used to collect qualitative data for triangulation and rationalization of the results. The findings indicated that students who memorized the multiplication tables performed better with and without calculators than those who did not memorize the multiplication tables. The findings also indicated that calculators did not help students who did not memorize the multiplication tables to improve their performance. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]