Series – Quick & Easy Study Notes
(Tripura TET – Reasoning Ability)
1️⃣ What is a Series?
A series is a list of things that follow a hidden rule.
Think of it like a recipe: each next step is made from the previous one using a simple instruction.
Examples
- Numbers: 2, 4, 6, 8, … (add 2 each time)
- Letters: A, C, E, G, … (skip one letter each time)
2️⃣ Types of Series in Reasoning
| Type | What it Looks Like | Everyday Analogy |
|---|---|---|
| Number Series | 5, 10, 15, 20, … | A countdown of stairs – each step is 5 feet higher |
| Letter Series | B, D, F, H, … | The alphabet like a hopscotch board – you jump two letters each time |
| Word Series | Cat, Dog, Cat, Dog, … | A game of “Simon Says” – you repeat the pattern |
| Mixed Pattern | 1, 1, 2, 3, 5, 8, … (Fibonacci) | A growing garden – each plant is the sum of the two before it |
3️⃣ How to Crack a Series
- Look at the first few items – they give the clue.
- Find the rule – what change happens from one item to the next?
- Add or subtract a number
- Multiply or divide
- Skip letters
- Alternate between two patterns
- Apply the rule to the last shown item to get the next one.
- Check – does your answer fit the whole series?
Quick Analogy
Imagine you are following a recipe:
- First ingredient: 2 cups of flour.
- Rule: Add 1 cup each time.
- Next step: 3 cups, then 4 cups, etc.
4️⃣ Common Patterns (Very Simple)
| Pattern | How it Works | Tiny Example |
|---|---|---|
| Add a constant | +2, +2, +2 | 3, 5, 7, 9 |
| Subtract a constant | –1, –1, –1 | 10, 9, 8, 7 |
| Multiply by a constant | ×2, ×2 | 1, 2, 4, 8 |
| Divide by a constant | ÷2, ÷2 | 16, 8, 4, 2 |
| Add, then subtract | +3, –1, +3, –1 | 2, 5, 4, 7 |
| Alternating two rules | +2, –1, +2, –1 | 4, 6, 5, 7 |
| Skipping letters | A, C, E, G | A, C, E, G |
| Repetition | Cat, Dog, Cat, Dog | Cat, Dog, Cat, Dog |
| Sum of previous two | 1, 1, 2, 3, 5 | 1, 1, 2, 3, 5 |
5️⃣ Mini‑Practice Questions
| # | Series | Next Item | Why? |
|---|---|---|---|
| 1 | 2, 4, 6, 8, … | 10 | Add 2 each time |
| 2 | B, D, F, H, … | J | Skip one letter each time |
| 3 | 3, 9, 27, 81, … | 243 | Multiply by 3 each time |
| 4 | 10, 7, 4, 1, … | –2 | Subtract 3 each time |
| 5 | Cat, Dog, Cat, Dog, … | Cat | Repeat the pair |
6️⃣ Quick Tips for the Exam
- Don’t over‑think – most series use simple operations.
- Check the first three items – they usually hold the key.
- Look for alternation – sometimes the rule changes every other step.
- Use a pencil – write the rule next to the series; it keeps you organized.
- Practice – the more patterns you see, the faster you’ll spot them.
7️⃣ Summary
- A series is a list that follows a hidden rule.
- Types: numbers, letters, words, or mixed patterns.
- Solve by: observing first items → finding the rule → applying it → checking.
- Common patterns: add/subtract, multiply/divide, skip letters, repeat, or sum of previous items.
- Practice regularly and keep your reasoning short and clear.
Good luck with your Tripura TET preparation!