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Basic Arithmetic

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Basic arithmetic is the load-bearing layer of everything that comes after. Multiplication is repeated addition; division is repeated subtraction; long multiplication and long division are addition and subtraction with bookkeeping. Fluency in the four basic operations on whole numbers — and an honest understanding of why the algorithms work — turns the rest of K-8 math from a hill into a flight of stairs.

These lessons cover addition and subtraction at every level: single digits, two-digit numbers with and without carrying, three-digit numbers with regrouping and borrowing, four- and five-digit numbers when the bookkeeping starts to bite. We treat place value as a topic of its own (because if a learner doesn’t see why “37” means three tens and seven ones, addition with carrying never quite makes sense). We cover estimation and rounding because mental math is a real-world skill — knowing that 487 + 312 is “about 800” before you compute the exact answer prevents most arithmetic errors. And we cover the properties of addition and subtraction — commutativity, associativity, identity — early, because they make later algebra readable.

Every lesson opens with a plain definition, walks through worked examples on tangible quantities (apples, balloons, blocks), and finishes with practice problems whose full reasoning is shown — not just the answer.

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Illustration for the Basic Addition lesson on Math Lessons

Basic Addition

Learn basic addition with apples, blocks and number lines — the foundational K-1 lesson that makes finding the sum click for first-time learners.

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  • Illustration for the Properties of Addition lesson on Math Lessons
    Basic Arithmetic

    Properties of Addition

    The Commutative Property of Addition states that changing the order of the numbers being added does not change the sum. In other words:

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  • Illustration for the Properties of Subtraction lesson on Math Lessons
    Basic Arithmetic

    Properties of Subtraction

    Subtraction has different rules compared to addition. While addition has properties like commutative, associative, and identity, subtraction behaves…

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  • Illustration for the Repeated addition lesson on Math Lessons
    Basic Arithmetic

    Repeated addition

    Repeated addition is a fundamental math concept where the same number is added to itself multiple times. It serves as the foundation for understanding…

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  • Illustration for the Subtraction of Two and Three-Digit Numbers with Borrowing lesson on Math Lessons
    Basic Arithmetic

    Subtraction of Two and Three-Digit Numbers with Borrowing

    Subtraction is a fundamental arithmetic operation where we find the difference between two numbers. When subtracting larger digits from smaller ones within…

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  • Illustration for the Addition of two digit numbers lesson on Math Lessons
    Basic Arithmetic

    Addition of two digit numbers

    Addition is one of the most fundamental math operations, and learning to add two-digit numbers confidently opens doors to more advanced math concepts. Let’s…

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  • Illustration for the Addition with Regrouping lesson on Math Lessons
    Basic Arithmetic

    Addition with Regrouping

    Addition with regrouping is an essential math skill that helps us add numbers where the sum of the digits in a column is 10 or more. Let’s explore this…

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  • Illustration for the Basic addition with algebraic concepts lesson on Math Lessons
    Basic Arithmetic

    Basic addition with algebraic concepts

    Algebra is a fascinating branch of mathematics that allows us to solve problems involving unknown numbers. By combining basic addition with algebraic…

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  • Illustration for the Basic subtraction lesson on Math Lessons
    Basic Arithmetic

    Basic subtraction

    Subtraction is one of the four fundamental arithmetic operations, and it plays a crucial role in everyday life. Whether you’re calculating change at the…

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  • Illustration for the Counting by Fives lesson on Math Lessons
    Basic Arithmetic

    Counting by Fives

    Counting by fives means adding five each time as you count. You land on every fifth number. This method of counting is useful for learning multiplication,…

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  • Illustration for the Counting by Tens lesson on Math Lessons
    Basic Arithmetic

    Counting by Tens

    Counting by tens means adding ten each time as you count. You land on every tenth number. This method is useful for understanding place value,…

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  • Illustration for the Counting by Twos lesson on Math Lessons
    Basic Arithmetic

    Counting by Twos

    Counting by twos is a fundamental math skill that helps build a strong foundation for addition, multiplication, and number sense. It’s a simple yet powerful…

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