Mental Addition and Subtraction Strategies Within 100

Estimate and determine quantities of large collections using perceptual grouping, ten-structures, and benchmark anchors.

Identify, write, and apply ordinal numbers up to 100th to describe rank, sequential position, and relative order in structured situations.

Deconstruct and reconstruct two-, three-, and four-digit numbers using standard and non-standard groupings, manipulatives, and place-value logic.

Read, write, translate, and model numbers up to 1,000 using standard notation, word names, expanded form, open number lines, and Roman numerals I to XII.

Count forward and backward from any starting number within 1,000 by 2s, 3s, 5s, 10s, 20s, 25s, 50s, and 100s, connecting sequences to money and patterns.

Compare, order, frame between tens and hundreds, and determine relative distance of numbers up to 1,200 using relational symbols and balance reasoning.

Calculate sums and differences within 100 mentally with high fluency using decomposition, making tens, compensation, and number lines.

Add combinations of three and four two-digit numbers using associative grouping, making tens, and columnar algorithms.

Add two- and three-digit numbers within 1,000 using base-ten models, expanded form, partial sums, and standard vertical algorithms with single and double regrouping.

Subtract two- and three-digit numbers within 1,000 using base-ten models, open number lines, expanded decomposition, and standard vertical algorithms with single, double, and across-zero regrouping.

Solve single- and multi-step word problems involving addition and subtraction within 1,000, money, estimation, and missing-value equations.