Series Completion

• Identify the pattern/rule in a number or letter series.
• Find the missing term or the next term in a series.
• Recognise common series types: arithmetic (constant difference), geometric (constant ratio), and alphabet-position series.

1. Arithmetic series: each term differs from the previous by a constant amount (e.g., 2, 5, 8, 11 → +3 each time).
2. Geometric series: each term is multiplied by a constant ratio (e.g., 2, 4, 8, 16 → ×2 each time).
3. Alternating series: two interleaved patterns (e.g., 1, 10, 3, 8, 5, 6 → odd positions +2, even positions -2).
4. Alphabet series: letters follow their position in the alphabet (A=1, B=2, ... Z=26), often with a numeric pattern applied.

Find the next term: 3, 6, 12, 24, ?

Each term is double the previous term (x2).
24 x 2 = 48

• Assuming every series is arithmetic (always check for multiplication/division patterns too).
• Missing alternating patterns by only looking at consecutive terms.
• Forgetting that letter positions wrap after Z (though most school-level series don't require wrapping).

• Find the next term: 5, 10, 15, 20, ?
• Find the missing term: 1, 4, 9, 16, ?, 36 (hint: perfect squares)

Open the Practice tab for graded questions on Series Completion.