Students add and subtract multi-digit whole numbers through 1,000,000 using place-value reasoning, partial sums, and the standard algorithms, including regrouping across zeros. They estimate sums and differences, check results for reasonableness, and solve missing-value equations using the inverse relationship between addition and subtraction. They model and solve one-step, comparison, and multi-step word problems involving whole-number quantities with equations, bar models, or number lines.