1. What this chapter covers
Decoding (known in Hindi as Koot Vachan or Koot Bhedan) is the exact reverse process of coding: it is the art of deciphering and interpreting encrypted messages to recover the original word, meaning, or digit. In competitive examinations, decoding problems test whether you can work backward from a code to its underlying source by undoing shifts, comparing shared vocabulary, and analyzing substitution tables.
The core decoding tasks covered in this chapter are:
- Substitution Coding: Real-world words are renamed according to a chain of fictitious labels (e.g., 'water' is called 'rain', 'rain' is called 'tree').
- The Golden Distinction: Solving forward substitution (X is called Y) versus reverse substitution (X means Y).
- Chinese / Mixed Word Coding: Deciphering entire coded sentences (e.g., 'ka ma pa' = 'Book is good', 'ka da' = 'Good boy') using the systematic elimination and comparison method.
- Mixed Number & Symbol Coding: Numerical and symbolic sentence mapping (e.g., '1 2 3' = 'hot filtered coffee', '3 5 6' = 'very hot day').
- Matrix / Grid Coding: Identifying letters from two-dimensional coordinate tables using standard Row-then-Column notation.
- Conditional Deciphering: Deciphering complex codes under conditional branching rules based on vowels, consonants, and parity.
2. Substitution Coding and the Crucial Rule: "Is Called" vs "Means"
Substitution coding replaces everyday objects with fictional names. The golden rule to avoid traps is identifying whether the connector is "is called" or "means".
Case 1: "Is called" / "Is named" (Forward mapping)
$$\text{Real Object} \longrightarrow \text{Code Name}$$ - *Question:* If 'water' is called 'rain', 'rain' is called 'tree', and 'tree' is called 'sky', where do fruits grow? - *Step 1:* Identify the true real-world answer $\rightarrow$ Fruits grow on a **tree**. - *Step 2:* Look at what 'tree' is called $\rightarrow$ 'tree' is called **sky**. - *Answer:* **Sky**.Case 2: "Means" (Backward / Reverse mapping)
$$\text{Code Name} \longrightarrow \text{Meaning (Real Object)}$$ - *Question:* If 'red' means 'green', 'green' means 'yellow', and 'yellow' means 'blue', what is the color of fresh grass? - *Step 1:* Identify the true real-world property $\rightarrow$ Fresh grass is **green**. - *Step 2:* Ask: Which word *means* green? The statement says **'red means green'**. - *Answer:* **Red** (because Red carries the meaning of green).3. Chinese / Mixed Coding: The Elimination Method
In Chinese or Mixed coding, complete phrases are written in artificial syllables. Words and codes do NOT necessarily appear in identical sequential order. You must deduce mappings by comparing pairs of statements.
Example Walkthrough
1. **Statement 1:** `ka ma pa` = `Book is good` 2. **Statement 2:** `ka da` = `Good boy` 3. **Statement 3:** `ma so` = `Book read`Deduction Steps:
1. **Compare Stmt 1 and Stmt 2:** - Common word: **Good** - Common code: **ka** - Therefore: **Good = ka**. 2. **Compare Stmt 1 and Stmt 3:** - Common word: **Book** - Common code: **ma** - Therefore: **Book = ma**. 3. **Resolve remaining codes in Stmt 1:** - In Stmt 1 (`ka ma pa` = `Book is good`), `ka` is Good and `ma` is Book. - The remaining code `pa` must represent **is**. 4. **Resolve Stmt 2 and Stmt 3:** - In Stmt 2, `ka` = Good, so `da` = **boy**. - In Stmt 3, `ma` = Book, so `so` = **read**.4. Matrix Coding (Grid Coordinate System)
In Matrix problems, letters are presented inside one or two $5 \times 5$ grids. Rows and columns are numbered (e.g., 0 to 4 in Matrix I, 5 to 9 in Matrix II).
Standard Convention: Row First, Column Second (RC)
- A letter at **Row 2** and **Column 3** is coded as the two-digit number **23**. - A letter at **Row 4** and **Column 0** is coded as **40**.Competitive Exam Strategy: Backward Elimination
When a 4-letter word such as **ROAD** is tested across 4 multiple-choice options: 1. Check the coordinates of the **last letter** (D) across all four options first. Often 2 or 3 wrong options are eliminated immediately. 2. Check the third letter (A), then the second (O), and verify the first (R). 3. Backward elimination saves up to 70 percent of exam time compared to checking from left to right.5. Step-by-step practice problems
Practice 01
If 'water' is called 'rain', 'rain' is called 'tree', and 'tree' is called 'sky', where do fruits grow?
A. Sky B. Tree C. Rain D. Water
Practice 02
If 'white' is called 'blue', 'blue' is called 'red', and 'red' is called 'yellow', what is the color of human blood?
A. Yellow B. Red C. Blue D. White
Practice 03
If 'pen' is called 'pencil', 'pencil' is called 'eraser', and 'eraser' is called 'book', what is used to erase pencil marks?
A. Book B. Eraser C. Pencil D. Pen
Practice 04
If 'sky' is called 'star', 'star' is called 'cloud', and 'cloud' is called 'earth', where do birds fly?
A. Star B. Sky C. Cloud D. Earth
Practice 05
In a code: 'ka ma pa' means 'Book is good' and 'ka da' means 'Good boy'. What word does 'ka' represent?
A. Good B. Book C. is D. boy
Practice 06
In a code: 'nik ma de' means 'he has come' and 'de lit pa' means 'come over here'. What is the code for 'come'?
A. de B. nik C. ma D. pa
Practice 07
If 'red' means 'green', 'green' means 'yellow', and 'yellow' means 'blue', what is the color of fresh grass?
A. Red B. Green C. Yellow D. Blue
Practice 08
In a code: '1 2 3' means 'hot filtered coffee' and '3 5 6' means 'very hot day'. Which digit represents 'hot'?
A. 3 B. 1 C. 2 D. 5
Practice 09
If '7 8 6' means 'study very hard', '9 5 8' means 'hard work pays', and '6 4 5' means 'study and work', what is 'very'?
A. 7 B. 8 C. 6 D. 9
Practice 10
If 'train' is called 'bus', 'bus' is called 'tractor', and 'tractor' is called 'car', what is used to plough a field?
A. Car B. Tractor C. Bus D. Train
Practice 11
If 'pic vic nic' = 'winter is cold', 'to nic re' = 'summer is hot', and 're pic may' = 'winter and summer', what is 'cold'?
A. vic B. nic C. pic D. to
Practice 12
If 'finger' is called 'toe', 'toe' is called 'foot', and 'foot' is called 'thumb', where is a ring worn?
A. Toe B. Finger C. Foot D. Thumb
Practice 13
If 'pit na som' = 'bring me water' and 'tub od pit' = 'give me food', what does 'pit' represent?
A. me B. water C. bring D. food
Practice 14
If 'bat' is called 'racket', 'racket' is called 'football', which equipment is used to play cricket?
A. Racket B. Bat C. Football D. Shuttlecock
Practice 15
If '2 4 7' = 'spread red carpet' and '2 6 4' = 'one red carpet', what digits represent 'red' and 'carpet'?
A. 2 and 4 B. 2 and 7 C. 4 and 7 D. 6 and 4
Practice 16
If 'apple' is called 'orange', and 'orange' is called 'banana', which fruit provides fresh orange juice?
A. Banana B. Orange C. Apple D. Mango
Practice 17
If 'si po re' = 'books are old' and 'ti po ma' = 'man is old', what code represents 'old'?
A. po B. si C. re D. ti
Practice 18
If 'gold' means 'silver' and 'silver' means 'copper', which metal is known as Argentum in Latin?
A. Gold B. Silver C. Copper D. Iron
Practice 19
In a code: 'la pa ta' = 'birds fly high' and 'ta ma' = 'high mountain'. What is the code for 'high'?
A. ta B. la C. pa D. ma
Practice 20
In Matrix coding, if Row 2 and Column 4 contain 'M', what is the two-digit code for 'M'?
A. 24 B. 42 C. 20 D. 4
Practice 21
In Matrix coding, which letter position is checked first for the fastest elimination?
A. The last letter B. The first letter C. The middle letter D. Any random letter
Practice 22
If 'su re nik' = 'she is brave' and 'pi sor nik' = 'she is always smiling', what do 'she' and 'is' share?
A. 'nik' is common to both sentences B. 'su' is common C. 'pi' is common D. 'sor' is common
Practice 23
If '134' = 'good and tasty' and '478' = 'see good pictures', what digit represents 'good'?
A. 4 B. 1 C. 3 D. 7
Practice 24
If 'mno pqr stu' = 'heavy green tree' and 'stu vwx yza' = 'tree stands tall', what code represents 'tree'?
A. stu B. mno C. pqr D. vwx
Practice 25
If '4 8 1' = 'sky is blue' and '6 9 8' = 'sea looks blue', what digit represents 'blue'?
A. 8 B. 4 C. 1 D. 6
Practice 26
Condition: If first element is vowel and last is consonant, both are coded as '$'. Does 'APPLE' satisfy this?
A. No, because last letter E is a vowel B. Yes, perfectly C. Only first letter satisfies D. Invalid condition
Practice 27
If 'cpt dkr flv' = 'light bright sun' and 'dkr hmt zps' = 'sun gives energy', what code is 'sun'?
A. dkr B. cpt C. flv D. hmt
Practice 28
If '5 2 6' = 'sky is blue' and '2 4' = 'blue color', what digit represents 'blue'?
A. 2 B. 5 C. 6 D. 4
Practice 29
If a message was encoded with shift +3, what inverse shift decodes it back to plaintext?
A. Shift backward by -3 B. Shift forward by +3 C. Multiply by 3 D. Reverse the string
Practice 30
In a 5x5 Matrix, what is the coordinate of the element at Row 0, Column 0?
A. 00 B. 01 C. 10 D. 55
6. Solutions to practice problems
Answer 01
A. Sky. Fruits grow on a tree. In this code, 'tree' is called 'sky'. Hence, fruits grow on Sky.
Answer 02
A. Yellow. Human blood is red. In this code, 'red' is called 'yellow'. Thus, the answer is Yellow.
Answer 03
A. Book. An eraser is used to erase pencil marks. Here 'eraser' is called 'book'. Hence, Book.
Answer 04
A. Star. Birds fly in the sky. In the code, 'sky' is called 'star'. Therefore, birds fly in Star.
Answer 05
A. Good. The common code in both statements is 'ka', and the common word is 'Good'. Therefore, 'ka' = Good.
Answer 06
A. de. The word 'come' is common to both statements, and 'de' is the shared code. Hence, 'come' = de.
Answer 07
A. Red. With the keyword 'means', we identify which term means green. The statement says 'red means green'. Hence, Red.
Answer 08
A. 3. Digit 3 is common to both numbers, and 'hot' is common to both sentences. Thus, 3 represents 'hot'.
Answer 09
A. 7. From 1 & 2, 'hard' = 8. From 1 & 3, 'study' = 6. In statement 1, the remaining digit 7 represents 'very'.
Answer 10
A. Car. A tractor ploughs a field. Here 'tractor' is called 'car'. Hence, a Car is used.
Answer 11
A. vic. In 1 & 2, 'is' = nic. In 1 & 3, 'winter' = pic. In statement 1, the remaining code 'vic' represents 'cold'.
Answer 12
A. Toe. A ring is worn on a finger. In this code, 'finger' is called 'toe'. Hence, Toe.
Answer 13
A. me. Comparing both sentences, 'me' is common, and 'pit' is common. Therefore, 'pit' = me.
Answer 14
A. Racket. Cricket is played with a bat. Here 'bat' is called 'racket'. Thus, Racket.
Answer 15
A. 2 and 4. Both statements share 'red carpet' and digits 2 and 4. Hence, 2 and 4 represent red and carpet.
Answer 16
A. Banana. Orange juice comes from an orange. Here 'orange' is called 'banana'. Thus, Banana.
Answer 17
A. po. Common word is 'old' and common code is 'po'. Therefore, 'old' = po.
Answer 18
A. Gold. Argentum is Silver. Under the 'means' rule, we find which term means silver: 'gold means silver'. Hence, Gold.
Answer 19
A. ta. The common word is 'high' and common code is 'ta'. Hence, 'high' = ta.
Answer 20
A. 24. By the Row-then-Column convention, Row 2 and Column 4 forms '24'.
Answer 21
A. The last letter. Checking the last letter first eliminates incorrect choices rapidly in competitive exams.
Answer 22
A. 'nik' is common to both sentences. The code 'nik' is present in both sentences and represents one of the shared words ('she' or 'is').
Answer 23
A. 4. Digit 4 is common and 'good' is common. Thus, 4 = good.
Answer 24
A. stu. The shared word is 'tree' and shared code is 'stu'. Therefore, 'tree' = stu.
Answer 25
A. 8. The common word is 'blue' and common digit is 8. Hence, 8 represents blue.
Answer 26
A. No, because last letter E is a vowel. In APPLE, the last letter E is a vowel, not a consonant. Hence, the condition fails.
Answer 27
A. dkr. The common word is 'sun' and common code is 'dkr'. Therefore, 'sun' = dkr.
Answer 28
A. 2. The common digit between 526 and 24 is 2, corresponding to 'blue'.
Answer 29
A. Shift backward by -3. Decoding is the exact inverse of encoding: to undo a +3 shift, subtract 3 (-3).
Answer 30
A. 00. Row 0 and Column 0 yields coordinate '00'.
7. Quick revision pointers
- In Substitution Coding, determine whether the question uses 'is called' (answer with the next term) or 'means' (answer with the previous term).
- In Chinese / Mixed Coding, write down shared words and codes in pairs; eliminate confirmed items step-by-step.
- In Matrix Coding, remember the order: Row number first, Column number second.
- Use backward elimination (starting from the last letter) in Matrix multiple-choice options to save time.
- In Conditional Coding, verify all constraints (vowel/consonant, odd/even, position) before applying replacement rules.
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