Students learn to compare numbers to 20 using concepts of 'more,' 'less,' and 'equal,' and can arrange numbers in order from least to greatest or greatest to least. Comparing numbers helps develop understanding of quantity and prepares students for working with larger numbers.
Use objects to physically compare groups, number lines to visualize position, and practice saying sentences like "8 is more than 5" and "15 is less than 18."
You already know how to compare groups of objects — if one pile has more blocks than another, you can tell by looking or by counting. And you know how to count objects one-by-one to find out exactly how many there are. Comparing and ordering numbers takes those two skills and applies them to the numbers themselves, not just to physical objects. Instead of comparing two piles of blocks, you're comparing the numbers that represent them.
The key idea is that numbers have an order — a fixed sequence from smallest to largest. When you count "1, 2, 3, 4 ... 20," you're not just reciting a list; you're moving along a number line from less to more. A number that comes later in the count represents a bigger quantity. So 15 comes after 7 when you count, which means 15 is greater than 7. You don't have to collect 15 blocks and 7 blocks and compare the piles — you can just think about where each number lives in the sequence.
A number line is the visual tool that makes this concrete. Draw a line with 0 on the left and 20 on the right, with every number marked in order. Any number to the right of another number is greater; any number to the left is less. Comparing 12 and 17 becomes visual: 17 is to the right of 12, so 17 is greater. Ordering three or more numbers — say 5, 14, and 9 — means finding each one on the line and reading them from left to right: 5, 9, 14. The number line turns an abstract question ("which is more?") into a spatial one ("which is further right?"), and spatial questions are often easier to answer.
Watch out for a common trap: the way numbers look doesn't always match their size. The number 9 is a single digit, but it's greater than any single-digit number below it. The number 11 has two digits, which might look "bigger" on the page, but the important thing is its position in the counting sequence, not its visual appearance. What matters is always the quantity the number represents — and counting sequence (or the number line) is the reliable guide to that, not how the numerals look.