About Addition & Subtraction
Mathematics grows by connecting definitions, patterns, models, calculations, and proof. This page builds the topic from basic ideas toward applications and deeper reasoning.
Addition
Addition combines quantities.
Learn MoreSubtraction
Subtraction finds differences or removes amounts.
Learn MorePlace Value
Written algorithms rely on aligned place values.
Learn MoreRegrouping
Regrouping exchanges equal values between places.
Learn MoreInverse Operations
Addition and subtraction undo each other.
Learn MoreMental Math
Flexible strategies can be faster than writing.
Learn MoreEstimation
Estimation checks whether an exact answer is reasonable.
Learn MoreApplications
Sums and differences appear everywhere.
Learn MoreAddition
It can model joining groups, increasing an amount, or moving forward on a number line.
Subtraction
It can model taking away, comparison, or finding a missing distance.
Place Value
Ones combine with ones, tens with tens, and so forth.
Regrouping
Ten ones can become one ten, and one ten can be decomposed into ten ones without changing total value.
Inverse Operations
Inverse relationships help check answers and solve equations.
Mental Math
Making tens, compensation, doubles, and breaking numbers apart are common mental strategies.
Estimation
Rounding or using compatible numbers can reveal large calculation errors.
Applications
Money, scores, time, distance, inventory, and measurements all use addition and subtraction.