Adding Two-Digit Numbers Within 100

Understand tens and ones as place value units and compose and decompose two-digit and three-digit numbers up to 120 in standard and flexible ways.

Compare and order two-digit and three-digit numbers up to 120 using place-value reasoning, comparative terms, and comparison symbols (>, <, =).

Mentally find 1 more, 1 less, 10 more, and 10 less than any two-digit number and explain digit patterns without counting.

Add within 100 using concrete models, number lines, place-value strategies, and expanded column methods, composing a ten when needed.

Subtract multiples of 10 from multiples of 10 and subtract single digits from decade numbers using concrete models, number lines, and inverse addition relationships.