Number & Symbol Coding

🎯 Learning Objective

Map letters to digits from solved words and derive the code of a new word, including position-sum codes.

💡 Concept

• Words can be coded as digit strings: each letter gets one fixed digit — same letter, same digit, everywhere
• Two coded words with a COMMON letter let you unlock the digit map one letter at a time
• Digit order usually follows letter order — verify it using the common letter
• Position codes use A=1 … Z=26 directly, or their SUM: CAT = 3 + 1 + 20 = 24
• For a new word, reuse the mapped digits; only unseen letters need fresh work

🧮 Key Formulas

Same letter → same digit, everywhere

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Position-sum code: CAT = 3 + 1 + 20 = 24

✏️ Easy Example

Q. If A=1, B=2, C=3 … Z=26, what is the code for BAD?

1. B = 2, A = 1, D = 4
2. Write the digits in word order

Answer: 214

🇮🇳 Real-Life Example

NDLS means New Delhi and BBS means Bhubaneswar on every ticket — railway station codes are word-to-symbol coding the whole country already reads.

📝 Exam-Level Example

Q. If ROSE is coded as 6821 and PEN is coded as 315, what is the code for ROPE?

1. ROSE: R=6, O=8, S=2, E=1
2. PEN: P=3, E=1 (E matches ROSE), N=5
3. ROPE = R, O, P, E = 6, 8, 3, 1

Answer: 6831

📝 Exam-Level Example

Q. In a certain code, CAT = 24. Following the same rule, what is the code for DOG?

1. Test position sum: C + A + T = 3 + 1 + 20 = 24 — matches
2. DOG = 4 + 15 + 7

Answer: 26

🪄 Memory Trick

Hunt the repeated letter across the given words first — it anchors the whole digit map. If the code is one small number, test the sum of letter positions.

⚠️ Common Mistakes

• ❌ Giving two different digits to the same letter
• ❌ Assuming the digit order blindly instead of confirming with the common letter
• ❌ Using A=1 positions when the question has defined its own mapping

🏆 Exam Tips

• ✅ Write the letter–digit map as a small table before answering
• ✅ EJOTY makes position sums fast: T=20, O=15 instantly

📌 Summary

• Same letter = same digit, always
• Common letters unlock the mapping
• Small single-number codes → try the position sum
• Build the map first, then code the new word