Number-Number Coding

In Number-Number Coding section of reasoning ability, the candidate will have to observe and guess the hidden code of two or more sets of numbers. Once the parent code is known, the candidate will have to use this code to generate other numbers. Let us know more by solving some questions.

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Code Number To Number

A code is a ‘system of signals’ that can be understood by a specific intended audience only. Therefore, coding is a method of transmitting a message between the sender and the receiver without a third person knowing it. The Coding and Decoding Test are set up to judge the candidate’s ability to decipher the rule that codes a particular word/message and break the code to decipher the message. Let us see some solved examples of this type.


Part A

Q1: In a certain code language 24685 is written as 33776. How is 35791 written in that code? (Bank P. O. Exam, 1989)

a) 44826              b) 44880               c) 46682              d) 44682              e) None of these

Answer: The key to solving the number based coding question is to be mindful of not only the value of the numbers but also the place value. For example, in this question, the letters at odd places are one place ahead and those at even places are one place before the corresponding letter in the word.

So, in 35791, 3 is written as 4. Similarly, 5 will be written as 4 and 7 as 8. Also, 9 will be written as 8 and 1 as 0. Thus, we see that the number becomes 44880 and the correct option here is b.

Q2: In a certain code language 35796 is written as 44887. How is 46823 written in that code? (Bank P. O. Exam, 1991)

a) 57914                b) 55914             c) 55934               d) 55714             e) None of these

Answer: Here again, we will see what pattern is followed while mapping or coding 35796 to 46823. Clearly, in the code, the letters at odd places are one place ahead and those at even places are one place before the corresponding letter in the word.

The same pattern as in the previous question has been followed and we can see that 4 will be written as 5, 6 will be written as 5, and 8 will be written as 9. Also, 2 will be coded as 1 and 3 will be coded as 4. So. the code becomes 55914 and the correct option is b).


Part B

Q1: In a certain code, the number 12345 is coded as 36936. What will be the code for the number 99325?

A) 99966                     B) 33965               C) 78356               D) 37649         E) none of these

Answer: The two numbers can be obtained as follows:

If we take 1 and multiply it by 3 and repeat the same with all the other digits of the first number, we will have:

  • 1 gives 3
  • 2 gives 6
  • 3 gives 9
  • 4 gives 12 = 1+2 = 3
  • And 5 gives 15 = 1+5 = 6

Thus the new number we get will be 36936. Now that we know the key to the code, we can use the same rule to find the code for 99325. All we have to do is multiply each digit in 99325 by three and add the digits of the numbers that have more than one digit. Thus, we can write:

  • 9 when multiplied by 3, will give 27 = 2+7 = 9.
  • Also, 3 when multiplied by 3, will give 9.
  • And 2 will similarly yield 6.
  • 5 will give 15 = 1+5 = 6
  • Thus the new number that we will get is 99966 and the correct answer is A).

Q2: If in a certain system of code, the number 943 is coded as 27129. Then what will be the code for 12345 in this system of coding?

A) 86863             B) 2837637              C) 3691215              D) 46728               E) None of these

Answer: Let us take the first two numbers and try to figure out a rule or the key to this code from them. We have to find a rule that can change 943 to 27129. A hint here is that the number of digits is different. The first two digits of the second number i.e. 27 can be got from 9 by multiplying it with 3. If we multiply 4 by 3 we get 12 and similarly if we multiply 3 by 3 we get 9. So the number we get is 27129 which is the required number.

So let us see what we get when we use this code for 12345.

  • 1, when multiplied with 3, will give 3.
  • 2, when multiplied by 3, will yield 6.
  • Similarly, 3 will yield 9
  • And 4 will yield 12 and 5 will give 15.

Thus the number that we will get from this will be 3691215 and the answer is C). Similarly, there will be other questions in Number- Number coding but the trick is to break down the question or the code into simpler parts. Take the given information and try to figure out a connection between the given numbers or digits of one number with one or more of the digits of the second number. That way you can save time and improve accuracy.

Practice Questions For You

Q1: In a certain coded language 9999 is mapped as 8888. In the same language what can be the possible code for 11111?

A) 12345               B) 10000           C) 00000             D) 11110                E) none of these

Answer: C) 00000

Q2: A code when applied to the number 786 gives the number 7850. When the number 897 is mapped through the same code, the number that we will get will be?

A) 78750               B) 8960                 C) 8856          D) 9870           E) none of these

Answer: B) 8960

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16 responses to “Letter-Number Coding”

  1. Sahithi says:

    What the alphabets we get if we decide the numbers 11,15,22,24,32,32,35

  2. Himanshu says:


  3. Himanshu says:

    If the DRAW is 10 and RING is 12 what is REST?

  4. Puneet says:

    If REASON is coded as 015327.. how is DISC coded?

  5. abhishek says:

    this is a great article

  6. Gajendra says:

    How to decod in series

  7. Mohemmad Muddassir says:

    Just decode this in contact no

  8. TABASSUM says:

    If ROSTER is 96 aand LION is 44 then what is MOUSE ?

  9. Kyle says:

    What is a4 e1 t1 ?

  10. Khasimvali says:

    281@₹ %’-678( !()7&% Find

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