This book, Volume I, was written specifically for the Panhellenic Written Competition 2C/2022/ and is a fundamental and necessary aid on the subject of Macroeconomic quantities. The reader can conceptually delve into the economic phenomena of GDP, economic growth, the SOLOW model, the Cobb-Douglas model, etc. In addition, the multiple-choice questions aim to fully understand these economic phenomena. The structure of the book, the way of writing and development of the topic, enhance the rapid reading and understanding of the material by the reader. Specifically, the book includes: Complete theory of Macroeconomics concepts in an extensive analysis Simple diagrammatic analyzes and examples for easy understanding Published examples and diagrams from distinguished EU sources Previous years exam questions 225 multiple choice questions with relevant hints after each sub-section of the material to the immediate embedding of concepts and possible themes by the reader. Volume I covers the following topics in section 8, Macroeconomic Quantities and National Accounts: 8.1 Gross Domestic Product, 8.2 Per Capita GDP, 8.3 Rate of Economic Growth GDP, 8.4 Causes of GDP Growth and Factors of Production and 8.5 Gross National Income.