<![CDATA[Mathematics learning, particularly in multi-digit addition and subtraction, remains a challenge for second-grade elementary school students, as they often have difficulty understanding place value, regrouping, and borrowing techniques. The use of concrete learning media is necessary to help students understand abstract mathematical concepts. This study aims to analyze the effectiveness of the Number Line Board (Papan Garis Bilangan/PAGARI) in improving the mathematics learning outcomes of second-grade elementary school students on multi-digit addition and subtraction. This study employed a Research and Development (R&D) method using the ADDIE model. The research subjects consisted of 8 students in the limited trial and 18 students in the wider trial. Data on effectiveness were obtained from pre-test and post-test results and analyzed using the N-Gain score. The results showed that the students' average learning outcomes in the limited trial increased from 74.38 in the pre-test to 98.75 in the post-test, with an N-Gain score of 0.95, categorized as high. In the wider trial, the average learning outcomes increased from 62.78 in the pre-test to 87.78 in the post-test, with an N-Gain score of 0.67, categorized as moderate. These results indicate that PAGARI is effective in improving the mathematics learning outcomes of second-grade elementary school students in multi-digit addition and subtraction. The use of PAGARI provides students with concrete and manipulative learning experiences through the integration of a number line, number sticks, question cards, and components for performing multi-digit arithmetic operations, thereby helping students understand arithmetic concepts and procedures in a more meaningful way.]]>
