Mathematics in Economics: Consumption and Saving Functions from the Perspective of the Islamic Green Economy

Abstract

This study aims to identify the consumption and saving functions of students at Syech M. Djamil Djambek State Islamic University of Bukittinggi within the framework of the Islamic Green Economy principles wasathiyyah (moderation), qana’ah (contentment), israf (extravagance), and tabdzir (wastefulness). The research adopts a descriptive quantitative approach with a population of 11,462 students and a sample of 100 respondents selected through purposive sampling based on the criteria of being active students with a steady source of income. Data were collected using questionnaires and analyzed through descriptive and quantitative methods employing a simple linear consumption and saving function model. The results indicate the consumption function C = 67 + 0.9861Y and the saving function S = –67 + 0.0139Y. The average student income was IDR 871,200, with consumption averaging IDR 859,100 and savings IDR 12,100. The findings reveal a positive relationship between income, consumption, and savings, with consumption showing a higher growth tendency compared to savings. From the Islamic Green Economy perspective, the study highlights the importance of managing income wisely, avoiding excessive consumption, and saving as an expression of both economic and spiritual responsibility. Implementing the principles of wasathiyyah and qana’ah helps balance needs and savings, fostering more sustainable and Islamically aligned economic behavior. The study concludes that the consumption and saving functions reflect the mathematical relationship among economic variables and serve as instruments for shaping balanced, independent, and beneficial economic behavior among students, consistent with the principles of the Islamic Green Economy.