TNPSC GROUP IV – DAY 25
Date: 06 November 2026 Time: 04:00 PM Category: TNPSC Grp IV
எண் மற்றும் எழுத்துத் தொடர்கள் – Number & Letter Series
1. Number Series
A number series is a sequence following a mathematical pattern.
Example:
2, 4, 6, 8, ?
Each term increases by 2.
Answer: 10.
2. Important Types
Addition
5, 10, 15, 20, ? Answer: 25 (+5).
Subtraction
50, 45, 40, 35, ? Answer: 30 (−5).
Multiplication
3, 6, 12, 24, ? Answer: 48 (×2).
Division
160, 80, 40, 20, ? Answer: 10 (÷2).
Square series
1, 4, 9, 16, 25, ? Answer: 36 (6²).
Cube series
1, 8, 27, 64, ? Answer: 125 (5³).
3. Increasing Differences
2, 5, 10, 17, 26, ?
Differences: +3, +5, +7, +9.
Next difference: +11.
26 + 11 = 37.
Answer: 37.
4. Letter Series
Alphabetical positions:
A = 1, B = 2, C = 3 ... Z = 26.
A, C, E, G, ?
Positions: 1, 3, 5, 7.
Next position: 9.
Answer: I.
5. Fully Worked Examples
Example 1
3, 7, 13, 21, 31, ?
Differences: 4, 6, 8, 10.
Next difference: 12.
31 + 12 = 43.
Answer: 43.
Example 2
4, 12, 36, 108, ?
Each term is multiplied by 3.
108 × 3 = 324.
Answer: 324.
Example 3
B, E, H, K, ?
Positions: 2, 5, 8, 11.
Increase by 3.
Next position: 14.
Answer: N.
Example 4
2, 10, 4, 20, 6, 30, ?
Odd-position terms: 2, 4, 6, 8.
Even-position terms: 10, 20, 30.
Answer: 8.
6. Examination Shortcuts
1. Calculate consecutive differences. 2. Check addition and subtraction. 3. Check multiplication, division, squares and cubes. 4. Separate alternating terms. 5. Convert letters to alphabetical positions. 6. Verify the pattern against all given terms.
Book-Back Progress
Related subject: Samacheer Kalvi Mathematics, Classes 6–10.
Exact chapter and exercise mapping: source not yet verified.
Original worked examples: 4. Verified PYQs: 0. Verified book-back questions: 0.
Push Notifications
Tamil title: 🔢 குரூப் 4 நாள் 25 – எண் மற்றும் எழுத்துத் தொடர்கள்!
Tamil message: கூட்டல், பெருக்கல், வர்க்க எண்கள், எழுத்துத் தொடர்கள்! 4 முழுத் தீர்வுகளுடன் தமிழ்–ஆங்கிலத்தில் கற்போம்.
English title: Group IV Day 25 – Number & Letter Series
English message: Learn number patterns, squares, cubes, alternating series and alphabetical sequences with four worked examples.