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Reasoning Tricks to Solve Coding -Decoding and Calendar Problems

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In this article, I am going to share very important Reasoning Ability tricks. These tricks will help you in solving reasoning ability questions very quickly. As this portion is the life and soul of all types of competitive exams. 

1. Coding -Decoding –   

This section is one of the most common sections included in all the types of competitive exams basically designed for hiring processes and higher education. Many candidates find Coding-Decoding questions challenging to solve, and as a result, they avoid attempting these scoring questions and lose some easy and quick marks.

So, here I have shared a very basic and important trick that will help you in boosting confidence in this topic.

One must remember the values of A-1, B-2, C-3, D-4, E-5,……………X-24, Y-25, Z-26.

So, for finding the reverse value of any number simply, subtract that no. from 27 

 Ex:- the reverse of A i.e 1 is  27-1 =26 so, our answer is Z whose value is 26. 

This concept will be very helpful in solving problems of Coding-Decoding.

Some Important types of Coding-Decoding concepts are mentioned below – 


Letter Coding is a type in which the letters are replaced with other letters.

Take an example of Letter Coding:

JUNE is coded as “HSLC”, then what should be the code for JULY.

Explanation: To solve these kinds of problems, you have to remember that every alphabet has a specific number.

So, according to the question,

JUNE is coded as “HSLC”

J is coded as 10, U is coded as 21, N is coded as 14 and E is coded as 5

In the same way, “HSLC” is coded as

H is coded as 8, S is coded as 19, L is coded as 12 and C is coded as 3

If you observe both the given word, it is coded by decreasing 2 for each alphabet.

So, in the same way, to code “JULY”, the same number should be decreased.

So you code “JULY” as:

J is coded as 10, U is coded as 21, L is coded as 12, Y is coded as 25

So, in the same way, it decreased each alphabet by 2

The final solution for JULY would be 8, 19, 10, 23

And you should code the word as “HSJW”.


Let us Understand it with the help of an Example 

If “GEEKS” is coded as 35542, and GAME is coded as 3895, then what would be the code for  SKEEG?

So, here  The code of every letter is already specified in the question itself, so no need to use fixed codes of the letters.

Now, specify the number of each letter to solve the problem. If you observe the two words, some of the letters are repeated, so no need to write the repeated letters.

Now, code the letters.

G is coded as 3, E is coded as 5, K is coded as 4, S is coded as 2, A is coded as 8, and M is coded as 9

Using these codes, “SKEEG” is coded as 2,4,5,5,3. 

2. Calendar –  

Likewise Coding-Decoding, this topic is very very important for many competitive exams as well as from the placement exam perspective. This topic seems to be a bit hard, but the tricks I am going to share will really make this topic very very easy.

So, the types of problems asked by the examiner are,

1. Given a month, date, and year. Use this data to find the week of the day.

2. Given a day, with its date. Find which day will be after x month or x days or x years. 

Before moving to the problems, One needs to learn the codes for the day, month, and year. These are,

For Years 
If the year is 1600-1699 then its code is 6
If the year is 1700-1799 then its code is 4
If the year is 1800-1899 then its code is 2
If the year is 1900-1999 then its code is 0 
If the year is 2000>= then its code is  6
Month Code for (Non-Leap Year) 
January - 0 
February - 3 
March - 3 
April - 6
May - 1
June - 4
July - 6
August - 2
September - 5
October - 0
November - 3
December - 5

Month Code for (LEAP YEAR)

January - 6
February - 2 
March - 3 
April - 6
May - 1
June - 4
July - 6
August - 2
September - 5
October - 0
November - 3
December - 5
For Week-Days  - 
Sunday - 0
Monday - 1
Tuesday - 2
Wednesday - 3
Thursday - 4
Friday - 5
Saturday - 6

Let us Understand them with the help of small and easy tricks.

1. Suppose we have given a date like 25 May 2003. and we have to calculate the day for this.

Step-1 = last 2 digits of a year 
Step-2 = month code 
Step-3 = Date
Step-4 = last 2 digits of year divided by 4(quotient)
Step-5 = Year code
Now add all these and find its remainder with 7.
Now, whatever the value you are getting convert it into Week Day Code and We will get the required Day.

Solving the above example –

 Step -1 The last 2 digits of a year is 03 i.e  3

Step -2 month code for May is  1

 Step -3 Date is 25

 Step -4 The last 2 digits divided by 4 is  0 i.e  3/4 gives quotient as 0 

 Step -5 Year code is 6

Adding them ( values obtained after all the 5 steps ) we get  (3 +1 + 25 + 6 + 0) = 35 

So, 35/7 = 0(Rem) 

And I have already mentioned in Trick’s section that  0 is the Code for Sunday. So, the Weekday on 25 May 2003was Sunday.

Hence it was Sunday on 25 May 2003

 2. Given a day, with it’s date. Find which day will be after x month or x days or x years. 

Before Moving toward the second type of question, One must know the basic things –

Number of days in January  31

The number of days in February 29 (leap year), 28 non-leap year. 

Number of days in March  31

Number of days in April  30

Number of days in May  31

Number of days in June 30

Number of days in July  31

Number of days in August  31

Number of days in September  30

Number of days in October 31

Number of days in November 30

Number of days in December  31

Now, moving towards the second type of question’s asked from Calendar Topic –


Que 2. It was Monday on 15th October 1923. What was the day on 17 November 1923?

TRICK --   So, we simply have to add the day's between two given date. and add it to the code of the day given
           in question and divide it by 7 to get the remainder .

i.e  16 days  from 15th October to 31 October 

 17 days from 1 November to 17th November

adding them we get  (16+17 ) = 33 days and dividing by 7 to it we get 5 as the remainder. 

Now, add 5 to the Code of Monday ( I have already mentioned in the TRICKS)  and divide it by 7 to get the remainder. i.e (5+1)/7 remainder is 6.

Now, Convert that remainder to corresponding weekdays to get the day on 17th November 1923.

So, 6 is the Code for Saturday.

Hence it was Saturday on 17th November 1923.


PRACTISE SET (Mixed questions on Coding-decoding and Calendars ) –


Que 1. What day of the week would be on 2nd October 1994 ?

Explanation:  According to the above rule 

Step : 1  last 2 digit of a year is 94 

Step : 2 month code for October is 0

Step : 3 Date is 2

Step : 4 last 2 digit divided by 4 is 23

Step : 5 Year code is 0 

Adding them we get  (94+0+2+23+0) =119 

So, 119/7 =0 rem 

And I have already mentioned in Trick’s section that  0 is the Code for Sunday. So, the Week day on 2nd October 1994 was Sunday.

Hence it was Sunday on 2nd October 1994.

 Que 2. It was Monday on 20th march 1882 , what would be day on 20th june 1882 ?

Explanation:  Simply we have to count the number of days from 20th march to 20th june 1882.

So, there are 11 days from 20th march to  31th march

30 days from 1st April to 30th April

31 days from 1st May to 31st May

20 days from 1st june to 20th june

So, Finally adding them we get  11 + 30 + 31 + 20 = 92

so, taking remainder of 92 with 7 gives 1 . and  adding 1 to the Code of week day given in question i.e ( code for Monday is 1)   gives(1+1 =2) which is the code for  Tuesday.   (THIS IS WHAT I HAVE MENTIONED IN  THE  ABOVE TRICKS)

Hence it was Tuesday on 20th June 1882.

Que 3. If   VGMACQ is coded as WHNCDR, then what will be the code for MOTHER ?

Explanation: So, observing pattern we can see that , Each consonant like (V,M,C,Q) is increased by 1 i.e V to W , M to I  

and each Vowel is increased by 2 i.e A to C    

So, applying the same

MOTHER can be written as NQUIGS

Here consonant like(M,T,H,R) is incremented by 1 i.e M to N, T to U   and Vowels i.e O,E is incremented by 2 , i.e O to Q , etc.

Que 4. If A=1 and  BAD is written as 214 , then what will be the code for ACE ?


Here we can see that every alphabet is written as it’s value in alphabets.

i.e A is the 1st alphabet.  so written as 1.

B is the 2nd, A is the 1st , D is 4th. So, written as 214.

So, ACE is written as 135. as A,C,E are the 1st , 2nd and 5th alphabet.

Que 5. If GEEKS is Written as  202222168 , then how would GOOD  be written ?


Here, we can observe that every alphabet’s reversed values is coded .

i.e G’s alphabet value is 7 and reversed  value is 27-7 =20.

E’s alphabet value is 5 and reversed  value is 27-5 =22.   and similarly for all.

So, GOOD will be written as  20121223

as     G’s alphabet value is 7 and reversed  value is 27-7 =20.

O’s alphabet value is 15 and reversed  value is 27-15 =12.

D’s alphabet value is 4 and reversed  value is 27-4 =23.  

Last Updated : 23 Sep, 2022
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