Students count, recognize, write, and represent whole-number quantities from 0 through 100, including one-to-one counting of objects, zero, counting forward from any number through 120, and counting backward from 20 or 100 to 0. They compose, decompose, and identify two-digit numbers through 99 as tens and ones, understand that ten ones make one ten, and count by 2s, 5s, and 10s through 100. They compare and order quantities and numerals through 100, identify numbers before, after, and between within 0–120, locate missing and given numbers on number lines, recognize odd and even quantities through 20, and estimate collections of about 20 or fewer objects.