Skip-counting by 2s (2, 4, 6, 8, ...), 5s (5, 10, 15, ...), and 10s (10, 20, 30, ...) shows multiplication patterns. Counting by 3s models 3 × 1, 3 × 2, 3 × 3, etc. Number lines and 100-charts visualize these patterns.
You already know how to skip-count by 2s, and you know that multiplication means equal groups. Now you can see that these two ideas are the same thing in different clothing. When you skip-count by 3s — 3, 6, 9, 12, 15 — you are listing the answers to 3 × 1, 3 × 2, 3 × 3, 3 × 4, 3 × 5. Every step in the skip-count sequence is one more equal group added. The skip-count sequence for any number is simply that number's multiplication table written out in order.
A 100-chart makes this pattern visible. If you shade every number you land on when skip-counting by 2s, you get a striped pattern: every even column is shaded. Skip-counting by 5s shades the 5-column and 10-column — the two columns that correspond to multiples of 5. These visual patterns are not just pretty: they show you that multiples of 2 always end in 0, 2, 4, 6, or 8, and multiples of 5 always end in 0 or 5. Those digit patterns are shortcuts for checking your multiplication and for identifying multiples at a glance.
On a number line, each hop in a skip-count sequence is the same size. Counting by 4s makes equal hops of 4: land on 4, then 8, then 12, then 16. This is a direct visual of the equal-groups model you learned earlier. Understanding skip-counting as a pattern also prepares you for arithmetic sequences later in math, where you analyze any sequence that grows by a constant amount — skip-counting sequences are the simplest and most familiar examples of that structure.