Coding-Decoding PYQs for UPSC (2011-2024) | Solved Questions & PDF Download

Practicing PYQs helps you understand the exam pattern, difficulty level, and frequently asked questions. Let’s dive into the year-wise questions!

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Year-Wise Coding-Decoding PYQs (2011-2024)

Q1. A military code writes SYSTEM as SYSMET and NEARER as AENRER. Using the same code, FRACTION can be written as [CSAT 2016]

(a) CARFTION

(b) FRACNOIT

(c) NOITCARF

(d) CARFNOIT

Solution:

Given that,

SYS(TEM) as SYS(MET)......reversing the last 3 alphabets as first three would give same result

(NEA)RER as (AEN)RER..... reversing the first 3 alphabets as last three would give same result

So (FRAC)(TION) -----(CARF)(NOIT)

Thus reversing the alphabets the code is written as CARFNOIT

Hence option (d) is correct

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Q2. In a certain code, '256' means 'red colour chalk', '589' means 'green colour flower' and '254' means 'white colour chalk'. The digit in the code that indicates 'white' is [CSAT 2017]

(a) 2

(b) 4

(c) 5

(d) 8

Solution:

Given that,

'256' - 'red colour chalk'

'589'- 'green colour flower'

'254' - 'white colour chalk'

From the above given code comparing 256 and 589 the common is 5 and colour so 5 indicates colour

Comparing 256, 589 and 254

2 - chalk, 5 - colour and 4 - white

Hence option (b) is correct

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Q3. If RAMON is written as 12345 and DINESH as 675849, then HAMAM will be written as [CSAT 2018]

(a) 92233

(b) 92323

(c) 93322

(d) 93232

Solution:

Given that,

RAMON - 12345

DINESH - 675849

From the above code

HAMAM - 92323

Hence option (b) is correct

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Q4. If LSJXVC is the code for MUMBAI, the code for DELHI is [CSAT 2018]

(a) CCIDD

(b) CDKGH

(c) CCJFG

(d) CCIFE

Solution:

Given that,

M - 1 = L, U - 2 = S, M - 3 = J, B - 4 = X, A - 5 = V and I - 6 = C

Thus on similar pattern DELHI is written as

D - 1 = C, E - 2 = C, L - 3 = I, H - 4 = D, I - 5 = D

CCIDD

Hence option (a) is correct

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Q5. If every alternative letter of the English alphabet from B onwards (including B) is written in lower case (small letters) and the remaining letters are capitalized, then how is the first month of the second half of the year written? [CSAT 2019]

(a) JuLY

(b) jULy

(c) jUly

(d) jUlY

Solution:

Given that,

Every alternative letter of the English alphabet from B onwards (including B) is written in lower case (small letters) and the remaining letters are capitalized

So, letters are

A, b, C, d, E, f, G, h, I, j, K, l, M, n, O, p, Q, r, S, t, U, v, W, x, Y, z

The first month of the second half of the year = jUlY

Hence option (d) is correct

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Q6. The letters from A to Z are numbered from 1 to 26 respectively. If GHI = 1578 and DEF = 912, then what is ABC equal to? [CSAT 2020]

(a) 492

(b) 468

(c) 262

(d) 246

Solution:

Given that,

GHI = 1578

DEF = 912

Alphabetically

GHI = 789, DEF = 456 and ABC = 123

GHI x 2 = 1578, DEF x 2 = 912 and ABC x 2 = 246

Hence option (d) is correct

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Q7. What is the missing term @ in the following? [CSAT 2020]

ACPQ: BESU: MNGI: @

(a) NPJL

(b) NOJM

(c) NPIL

(d) NPJM

Solution:

Given that,

ACPQ: BESU

A + 1 = B, C + 2 = E, P + 3 =  S, Q + 4 = U

So, M + 1 = N, N + 2 = P, G + 3 = J, I + 4 = M

Thus the missing term = NPJM

Hence option (d) is correct

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Q8. In a code language 'MATHEMATICS' is as LBSIDNZUHDR'. How is 'CHEMISTRY' written in that code language? [CSAT 2021]

(a) DIDLHRSSX

(b) BIDNHTSSX

(c) BIDLHTSSX

(d) DGFLIRUQZ

Solution:

Given that,

'MATHEMATICS' ----- LBSIDNZUHDR' (it follows -1 and + 1 sequence)

CHEMISTRY ------ BIDNHTSSX

Hence option (b) is correct

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Q9. In the English alphabet, the first 4 letters are written in opposite order; and the next 4 letters are written in opposite order and so on; and at the end Y and Z are interchanged. Which will be the fourth letter to the right of the 13th letter? [CSAT 2021]

(a) N

(b) T

(c) H

(d) I

Solution:

Given that,

The first 4 letters are written in opposite order; and the next 4 letters are written in opposite order and so on.

At the end Y and Z are interchanged

Now,

Alphabets are ABCD EFGH IJKL MNOP QRST UVWX YZ

Written as DCBA HGFE LKJI PONM TSRQ XWVU ZY

4th letter from the right of 13th letter = 17th letter = T

Hence option (b) is correct

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Q10. If the order of the letters in the English alphabet is reversed and each letter represents the letter whose position it occupies, then which one of the following represents 'LUCKNOW? [CSAT 2022]

(a) OGXPMLD

(b) OGXQMLE

(c) OFXPMLE

(d) OFXPMLD

Solution:

Given that,

The English alphabet is reversed and each letter represents the letter whose position it occupies.

The reverse of the letters are:

A B C D E F G H I J K L M

Z Y X W V U T S R Q P O N

So LUCKNOW....... OFXPMLD

Hence option (d) is correct

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Q11. If 'ZERO' is written as 'CHUR', then how is 'PLAYER' written? [CSAT 2023]

(a) SOCAGT

(b) SODBGT

(c) SODBHT

(d) SODBHU

Solution:

Given that,

'ZERO' is written as 'CHUR'

So by decoding it Z + 3 = C, E + 3 = H, R + 3 = U and O + 3 = R

Similarly PLAYER is written as SODBHU

Hence option (d) is correct

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Q12. The letters of the word "INCOMPREHENSIBILITIES" are arranged alphabetically in reverse order. How many positions of the letter/letters will remain unchanged? [CSAT 2023]

(a) None

(b) One

(c) Two

(d) Three

Solution:

Given that,

"INCOMPREHENSIBILITIES" are arranged alphabetically in reverse order

Thus INCOMPREHENSIBILITIES is written as T S S R P O N N M L I I I I I H E E E C B

Therefore the positions of two I's remains the same.

Hence option (c) is correct

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Q13. If in a certain code, 'ABCD' is written as 24 and EFGH' is written as 1680, then how is 'IJKL' written in that code? [CSAT 2024]

(a) 11880

(b) 11240

(c) 7920

(d) 5940

Solution:

Given that,

ABCD = 24

EFGH = 1680

Now,

ABCD = 1 x 2 x 3 x 4 = 24

EFGH = 5 x 6 x 7 x 8 = 1680

Similarly,

IJKL = 9 x 10 x 11 x 12 = 11880

Hence option (a) is correct

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Q14. If in a certain code, 'POT' is written as ATOP and 'TRAP' is written as APART, then how is 'ARENA' written in that code? [CSAT 2024]

(a) AARENA

(b) AANREA

(c) AANEAR

(d) AANERA

Solution:

Given that,

POT = ATOP

TRAP = APART

Now,

POT = ATOP

TRAP = APART

A is added and rest part is reversed

Similarly,

ARENA = AANERA

Hence option (d) is correct

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Q15. In some code, letters P, Q, R, S, T represent numbers 4, 5, 10, 12, 15. It is not known which letter represents which number. If Q-S=2S and T=R+S+3, then what is the value of P+R-T? [CSAT 2024]

(a) 1

(b) 2

(c) 3

(d) Cannot be determined due to insufficient data

Solution:

Given that,

P, Q, R, S, T represents 4, 5, 10, 12, 15

Q - S = 2S

T = R + S + 3

Now,

Q = 3S.....(i)

Two cases possible

either S = 4 or 5 and Q = 12 or 15

T = R + S + 3

If R = 10

Then T = 10 + 4 + 3 = 17

or T = 10 + 5 + 3 = 18

Both the cases are not possible as the numbers are 4, 5, 10, 12, 15

So R < 10

So either R = 4 or 5

If R = 4

T = 4 + 5 + 3 = 12 (Possible)

If R = 5

T = 5 + 4 + 3  = 12 (Not possible as S = 4 then Q = 12 so, T cannot be 12)

The values are

P = 10, Q = 15, R = 4, S = 5, T = 12

P + R - T = 10 + 4 - 12 = 2

Hence option (b) is correct

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ANSWER KEY

1.      D

2.      B

3.      B

4.      A

5.      D

6.      D

7.      D

8.      B

9.      B

10.  D

11.  D

12.  C

13.  A

14.  D

15.  B

 

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Download Coding-Decoding PYQs PDF

➡️ Download the complete set of Coding-Decoding PYQs (2011-2024) with solutions in PDF format.

➡️ Click Here to Download PDF

 

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FAQs on Coding-Decoding for UPSC

1. Is Coding-Decoding important for UPSC?

Yes, Coding-Decoding is a crucial topic for the UPSC CSAT paper. It tests your logical reasoning and analytical skills.

2. How to prepare for Coding-Decoding in UPSC?

· Understand basic concepts like letter coding, number coding, and pattern-based coding.

· Practice PYQs regularly.

· Use reliable resources like NCERT books and online platforms like iassetu.com.

3. What are the most frequently asked Coding-Decoding questions in UPSC?

· Letter and number coding

· Pattern-based coding

· Mixed coding problems

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Conclusion

Practicing Coding-Decoding PYQs is essential for cracking the UPSC CSAT paper. This page provides year-wise solved questions, practice problems, and a free PDF download to help you prepare effectively. Bookmark this page and revisit it regularly for updates.

For more UPSC preparation resources, explore iassetu.com. Happy learning!

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