Each term increases or decreases by a constant difference
5, 8, 11, 14 (difference = +3) 2
Each term is multiplied by a constant ratio
2, 6, 18, 54 (ratio = ×3) 3. Square/Cube Series: Based on squares or cubes of consecutive numbers
1, 4, 9, 16 (1², 2², 3², 4²) 4
Following prime number sequence 5
Combination of addition, subtraction, multiplication, division 6. Double/Triple Layer Series: Two or three different patterns running simultaneously
SSC CGL typically asks 2-3 questions on number series. Common question types include finding the missing term, identifying the wrong number, or completing the series. The difficulty ranges from simple arithmetic progressions to complex mixed operation patterns. Powerful Shortcut - The Difference Method: Write differences between consecutive terms. If first-level differences don't show pattern, find second-level differences (differences of differences).
Most SSC series get solved within 2-3 levels.
Find first-level differences 7-3 = 4 15-7 = 8 31-15 = 16 ? -31 = ? 127-? = ?
Observe the difference pattern 4, 8, 16, ?, ? This is a geometric series with ratio 2 Next difference = 16 × 2 = 32 Following difference = 32 × 2 = 64
Find the missing number ? = 31 + 32 = 63 Verify: 127 - 63 = 64 ✓ Answer: 63
for Square Series: If you see numbers like 2, 5, 10, 17, 26, check if they follow n² + 1 pattern: 1² + 1 = 2 2² + 1 = 5 3² + 1 = 10 4² + 1 = 17 5² + 1 = 26
Students often assume the first pattern they see is correct. Always verify your answer by checking if it fits the complete series. In mixed operation series, don't stop at first-level differences - go deeper if needed.
8graded MCQs · easy to hard · full solution & trap analysis