This lecture covers fundamental arithmetic operations including addition, subtraction, multiplication, and division with step-by-step explanations. It starts with multi-digit addition (with and without carry-over), applies addition to real-life word problems, and moves to subtraction (with and without borrowing) followed by practical scenarios. Multiplication is explained through vertical methods, times tables, and real-world applications, and division problems are solved using basic long division. Mental math strategies are also introduced to build calculation speed and accuracy.