Skip counting by 100s means adding 100 each time: 100, 200, 300, 400, … 1000. The hundreds digit increases by 1 each step while the tens and ones digits remain unchanged — just as skip counting by 10s changes only the tens digit. This pattern reinforces the structure of the base-ten system and builds readiness for mental addition and subtraction of hundreds.
Use a hundreds chart extended to 1000. Begin from 0 and count forward; then start from numbers like 250 and count forward or backward by 100. Connect to place-value blocks: adding one flat each time.
You already know how to skip count by 10s: 10, 20, 30, 40 … Each jump adds one ten, so the tens digit ticks up by one each time while the ones digit stays put. Skip counting by 100s works exactly the same way, one level up. Each jump adds one hundred, so the hundreds digit ticks up by one each time — while both the tens digit and the ones digit stay completely unchanged. If you start at 247 and count by 100s, you get 347, 447, 547, 647 — only the first digit changes.
This is a direct consequence of how place value works, your prerequisite knowledge. In our base-ten system, each place is worth ten times the place to its right. Adding 100 affects only the hundreds place because 100 is exactly one unit in that column. It is like adding one flat base-ten block each time: the stacks of rods and the individual cubes never change — only the count of flats grows. Seeing this with physical blocks makes the pattern obvious.
The sequence 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000 is the "skeleton" of three-digit numbers. It also sets you up for mental math: adding or subtracting 100 from any number is quick because you are just changing one digit. 638 + 100 = 738; 638 − 100 = 538. No carrying, no borrowing — just a one-digit update in the hundreds place. Practicing this sequence forward and backward, and starting from numbers other than zero (like 250, 350, 450 …), builds the flexibility you will need for that mental arithmetic and for understanding the number line up to 1000.