Finding the Common Difference (Grades 4–5)
In an arithmetic sequence, the gap between consecutive terms is constant — the common difference.
Understanding finding the common difference
Find it by subtracting any term from the one after it. Once you know the difference, you can extend the sequence forward or backward (a negative difference means it decreases).
Seeing it in action
Worked example
Find the common difference and next term: 2, 5, 8, 11, __.
Difference = 5 − 2 = 3. Next = 11 + 3 = 14.
The same gap repeats between terms.
A common mistake, and the fix
Subtracting in the wrong order, which flips the sign.
The difference is later minus earlier: in 2, 5, 8, 11 it is 5 − 2 = 3, so the next term is 14. In a falling sequence such as 20, 17, 14 the same subtraction gives 17 − 20 = −3, and the next term is 11.
Try a few
10, 7, 4, __ — difference and next?
1, 6, 11, __
20, 24, 28, __
Number Current
A calm number-line game for placing whole numbers and extending patterns.
Try it in Numeris.
A short lesson, then practice with feedback on every answer.
Put the reasoning on paper.
Try six fraction, angle, perimeter and area questions with explained answers, for grades 4–6.
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