Analogies, Classification and Odd-One-Out
The official CEN 08/2024 syllabus for General Intelligence & Reasoning opens with \"Analogies\" and, a few lines later, names \"Similarities and differences\" and \"Classification\". Those three phrases describe one skill wearing three costumes. In an analogy you are given a relationship and asked to rebuild it. In classification and odd-one-out you are given four items that already share a relationship and asked to find the one that does not. Learn to name a relationship precisely and both question types collapse into the same twenty-second drill. Note that the CEN itself says the topic list is illustrative and the section split only indicative, so treat the number of questions from any one topic as variable and check the live notice on the RRB portals such as rrbcdg.gov.in for the pattern that applies to your CBT. What does not vary is the method, and that is what this chapter teaches.
KarmSakha preparation topics covered
- Analogies — word, number, letter and mixed pairs (CEN 08/2024, General Intelligence & Reasoning)
- Similarities and differences
- Classification
- Odd-one-out, the form in which classification is most often asked in the CBT
Name the Relation Before You Look at the Options
An analogy gives you one complete pair and one half-pair: Cobbler : Shoe :: Mason : ? The pair is not there to test your vocabulary. It is there to define a relationship, and that relationship — not the words — is the real question. So the first move is never to read the options. The first move is to say the relationship out loud as one short sentence that contains both given words in the given order. For Cobbler : Shoe the sentence is "A cobbler makes shoes." For Ohm : Resistance it is "An ohm is the unit that measures resistance." For Bee : Hive it is "A bee lives in a hive."
Once that sentence exists, the question becomes a fill-in-the-blank. Put the third word into the same sentence and see which option completes it: "A mason makes ___." A mason makes a wall. Brick and cement are what a mason uses, not what a mason makes, so they fail the sentence even though they feel connected. This is the entire technique. Aspirants lose these marks not because the relation is hard but because they read the options first and pick whichever word feels closest to the third word.
Direction matters as much as the relation. Cobbler : Shoe and Shoe : Cobbler are different questions, and setters exploit this. In a four-option item, one distractor is very often the right idea placed in the reversed direction. Because your sentence contains the words in order, the reversal is caught automatically: "A wall makes a mason" is nonsense, so the trap never gets near you.
- Step 1 — Write the relation as one sentence containing both given words, in order.
- Step 2 — Substitute each of the four options into the same sentence.
- Step 3 — If two options survive, tighten the sentence until only one does (see the narrower-relation rule in the last section).
- Never start at the options. Starting at the options is what makes an easy question take ninety seconds.
The Twenty Relationships the Paper Keeps Reusing
Word analogies in Level-1 papers are drawn from a small, repeating pool of relationship types. You do not have to invent a relation from nothing each time — you have to recognise which of about twenty familiar shapes you are looking at. The table below gives each type with two examples. Read it as a recognition drill, not a memorisation list: cover the left column, look at a pair, and try to name its type.
Some pairs sit in more than one row. Cow : Milk is animal–product; Cow : Calf is animal–young. Doctor : Hospital is worker–workplace, while Doctor : Patient would be professional–person served. This is why the sentence matters. The sentence fixes which of the possible relations the setter actually intends, and it is built from the pair you were given, not from the options.
| Relationship type | Example 1 | Example 2 |
|---|---|---|
| Synonym (same meaning) | Brave : Courageous | Abundant : Plentiful |
| Antonym (opposite meaning) | Ancient : Modern | Expand : Shrink |
| Tool – worker who uses it | Scalpel : Surgeon | Chisel : Sculptor |
| Worker – what the worker makes | Baker : Bread | Weaver : Cloth |
| Part – whole | Nib : Pen | Petal : Flower |
| Individual – group (collective noun) | Sailor : Crew | Sheep : Flock |
| Cause – effect | Injury : Pain | Drought : Famine |
| Unit – quantity it measures | Ohm : Resistance | Hectare : Area |
| Animal – its young one | Cow : Calf | Goat : Kid |
| Animal – its home | Bee : Hive | Horse : Stable |
| Country – capital | Nepal : Kathmandu | Bhutan : Thimphu |
| Country – currency | Japan : Yen | Bangladesh : Taka |
| Raw material – finished product | Clay : Pot | Wheat : Flour |
| Instrument – quantity measured | Barometer : Atmospheric pressure | Ammeter : Electric current |
| Study – its subject matter | Ornithology : Birds | Seismology : Earthquakes |
| Word – higher degree of the same idea | Warm : Scorching | Dislike : Hate |
| Worker – workplace | Judge : Court | Chef : Kitchen |
| Object – its function | Knife : Cut | Broom : Sweep |
| Animal – its sound | Lion : Roar | Horse : Neigh |
| Container – what it holds | Granary : Grain | Quiver : Arrow |
Number Analogies: Test in a Fixed Order
Numbers carry no meaning, so the only thing that can link them is arithmetic. The danger is staring at 26 : 12 and hoping the rule appears. It will not. Instead, run a fixed checklist, cheapest test first, and stop at the first rule that fits. The order is: difference, then ratio, then powers (square, cube, and those plus or minus 1), then digit operations (digit sum, product of digits, reversal), then position in a known sequence such as the primes.
Working in this order matters because it takes about three seconds to subtract and three seconds to divide, while spotting that 728 is one less than 9³ takes longer. Do the cheap tests first and most questions end there. When you do reach the powers stage, you need squares up to at least 20² = 400 and cubes up to 12³ = 1728 available instantly; those tables are in the formula-sheet chapter and are worth five minutes of revision a day.
One discipline protects you from a wrong answer: after finding a rule, apply it to the third number and check that the result appears exactly once among the options. If two different rules both fit the given pair but produce different options, you have chosen too early — go back and find the rule that makes only one option correct. For 24 : 8, for example, both "divide by 3" and "multiply the digits" fit, so a well-set question will never use that pair; if you meet it, decide by which rule leaves a single valid option.
| Rule | Given pair | Why it fits | Same rule applied |
|---|---|---|---|
| Square, n → n² | 13 : 169 | 13 × 13 = 169 | 17 → 289 |
| Cube, n → n³ | 6 : 216 | 6 × 6 × 6 = 216 | 8 → 512 |
| Square minus one, n² − 1 | 12 : 143 | 144 − 1 = 143 | 15 → 224 |
| Cube minus one, n³ − 1 | 9 : 728 | 729 − 1 = 728 | 6 → 215 |
| n² + n, i.e. n(n + 1) | 5 : 30 | 25 + 5 = 30 | 8 → 72 |
| Constant added | 17 : 24 | 17 + 7 = 24 | 31 → 38 |
| Constant multiplied | 14 : 42 | 14 × 3 = 42 | 23 → 69 |
| Sum of the digits | 38 : 11 | 3 + 8 = 11 | 57 → 12 |
| Product of the digits | 26 : 12 | 2 × 6 = 12 | 47 → 28 |
| Digits reversed | 34 : 43 | the two digits swap places | 71 → 17 |
| Next prime in order | 7 : 11 | 7 is the 4th prime, 11 the 5th | 13 → 17 |
Letter Analogies: Write the Positions First
Every letter question becomes arithmetic the moment you write each letter's position underneath it. A = 1 through Z = 26. Counting from A each time is slow and causes errors under a 90-minute clock, so use the EJOTY landmarks — E = 5, J = 10, O = 15, T = 20, Y = 25 — and count a step or two forward or backward from the nearest one. R is two past O plus one more group, or simply T minus 2, giving 18.
Three families cover almost everything. First, block shift: all letters in the group move by the same amount. In CEG : IKM every letter moves +6, so PRT becomes VXZ. Second, individual shifts: each letter moves by its own amount in a pattern, such as +1, +2, +3 — CAT becomes DCW, so DOG becomes EQJ. Third, opposite letters: A pairs with Z, B with Y, and so on. Since A is 1 and Z is 26, and 1 + 26 = 27, every letter and its opposite have positions adding to 27. So the opposite of a letter at position n sits at position 27 − n. F is 6, so its opposite is at 21, which is U.
Do the internal gaps before the external shift. Look at the given group by itself and note the gaps inside it (C→E→G is +2, +2). Then compare the given group with its partner to get the shift. Keeping these two measurements separate is what stops you from mixing a +2 internal gap with a +6 external shift and producing a letter that is off by four places.
| Letter | Position | Opposite letter | Its position |
|---|---|---|---|
| A | 1 | Z | 26 |
| B | 2 | Y | 25 |
| C | 3 | X | 24 |
| D | 4 | W | 23 |
| E | 5 | V | 22 |
| F | 6 | U | 21 |
| G | 7 | T | 20 |
| H | 8 | S | 19 |
| I | 9 | R | 18 |
| J | 10 | Q | 17 |
| K | 11 | P | 16 |
| L | 12 | O | 15 |
| M | 13 | N | 14 |
Classification and Odd-One-Out: Find the Property Exactly Three Share
Classification is the analogy method run backwards. Instead of being handed a relation, you must discover it — and you discover it from the majority. Look at the four items, find a property that is true of three of them, and the fourth is your answer. State that property as a sentence, the same as before: "These are pure metals", "These are perfect cubes", "These triplets have gaps of +2 and +2."
For words, test in this order: category (all are vegetables), function (all measure electrical quantities), origin or composition (all are elements, not mixtures), and source (all grow underground). For numbers, test perfect squares, perfect cubes, primes, divisibility by a common factor, digit sum, and digit patterns such as reversal or repeated digits. For letter clusters, write the positions and take the first differences; the odd cluster is the one whose difference row breaks the pattern, or the pair whose positions do not sum to 27 when the others do.
The discipline that decides hard items is the phrase exactly three. A property that is true of all four items is not the answer property — it is a distraction. In the set 64, 125, 216, 196, the property "perfect square" is true of 64 (8²) and 196 (14²) but not of 125 or 216, so it covers only two and is rejected. The property "perfect cube" is true of 64 (4³), 125 (5³) and 216 (6³) but not 196. That covers exactly three, so 196 is the odd one. Always ask how many items your candidate property covers before you commit.
| Set type | Properties to test, in order | Worked check |
|---|---|---|
| Words | Category → function → composition → source | Copper, Zinc, Bronze, Nickel: three are pure metals, bronze is an alloy of copper and tin → Bronze |
| Numbers | Square → cube → prime → common divisor → digit sum → digit pattern | 17, 27, 37, 47: three are prime, 27 = 3 × 3 × 3 → 27 |
| Letter triplets | Internal gaps from the position row | BDF, HJL, MOQ, RTW: gaps are +2,+2 except RTW which is +2,+3 → RTW |
| Letter pairs | Sum of the two positions; opposite-letter test | AZ, BY, CX, DV: sums are 27, 27, 27, 26 → DV |
Tie-Breaks, Standard Traps and Timing
When two options both satisfy your sentence, the rule is to choose the narrower relation — the one that is true of fewer pairs in the world. Take Doctor : Hospital :: Teacher : ? with Student and School among the options. A teacher is genuinely connected to a student. But the sentence built from the given pair is "A doctor works in a hospital", which is worker–workplace, and the option that fits worker–workplace is School. Student would fit a different relation (professional–person served) that the given pair does not display. Narrower means: the relation that uses more of the information in the given pair.
Four traps account for most avoidable losses here. The reversed pair, already discussed. The near-miss of degree, where the option is in the right direction but the wrong intensity. The odd-one-out where two items share a surface feature — all four numbers ending in 7, say — while the real property is primeness. And the letter question answered by counting from A on your fingers, which produces an answer one place out; positions written on the rough sheet remove this completely.
