Completing a Skip Counting Table

A skip counting table lists numbers that follow a steady pattern, but a few of the numbers are missing. To complete the table, you need to figure out the "jump" between the numbers that are already there, and then use that same jump to fill in every empty spot. This is the same idea behind counting by 2s, 5s, or 10s, just organized into a table instead of a plain list.

Skip counting tables show up everywhere once you start counting groups of objects, reading number grids, or working with early multiplication ideas. Before tackling this lesson, it helps to be comfortable with number sequences with 1, 2, 3, 5, 10, since a skip counting table is really just a sequence written in boxes.

Look at two numbers that sit next to each other in the table, where both values are already given. Subtract the smaller number from the larger one. That difference is the counting rule, the amount you add each time you move one spot to the right.

For example, if the table shows 5 and then 10 in the very next spot, the rule is \( 10 - 5 = 5 \). That tells you the table is skip counting by 5.

One pair of numbers is a good start, but it is safer to check the rule against a second known pair before filling anything in. In the table above, look at position 2 (10) and position 4 (20). Since two spots separate them, the jump should be double the rule, or \( 5 + 5 = 10 \), and \( 10 + 10 = 20 \) confirms it. When both checks agree, you know the counting rule for the whole table.

Once the rule is confirmed, work through the table from left to right. Add the rule to the last known number to get each new value, and use that answer to find the next one.

• Position 3: \( 10 + 5 = 15 \)
• Position 5: \( 20 + 5 = 25 \)

The completed table reads 5, 10, 15, 20, 25, 30, each number exactly 5 more than the one before it.

Sometimes the missing box comes right before a number you already know, rather than after it. In that case, subtract the rule instead of adding it. If the rule is 5 and the number right after the blank is 20, then the missing number is \( 20 - 5 = 15 \). This works the same way whether the table counts up by 2s, 5s, or 10s.

Most skip counting tables at this level use one of a few familiar rules:

• Counting by 2s: 2, 4, 6, 8, 10, ... (every value is even)
• Counting by 5s: 5, 10, 15, 20, 25, ...
• Counting by 10s: 10, 20, 30, 40, 50, ...

Noticing whether the values are even or odd can also give you a quick check on your work. If you want extra practice spotting that pattern, see identifying a number as even or odd. Skip counting tables are also closely related to number grids, where you fill in missing values across rows and columns; that skill is covered separately in missing values in a number grid up to 100.

• Always find the rule from two numbers that are already filled in, never guess it from a blank.
• Double-check the rule with a second pair whenever the table gives you enough information.
• Move through the table in order so each answer builds on the one before it.
• After finishing, re-add the rule across the whole table once more to make sure every jump matches.

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• Math 1