UPSC CSE Prelims CSAT (Paper II) previous year questions on Coding Decoding (Logical Reasoning), asked from 2016–2026, with answers. There are 15 questions in this post. Attempt each question, then click Show Answer to check.
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1] If ZERO is encoded as ADSN, then how do you encode STOP? [2026/67]
(a) SPOT
(b) TSPO
(c) TSOP
(d) POST
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Ans: (b) TSPO
2] If 7 * 24 = 25 and 12 * 16 = 20, then what is 16 * 63 equal to? [2025/16]
(a) 70
(b) 66
(c) 65
(d) 64
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Ans: (c) 65
3] If NO is coded as 210, NOT as 4200 and NOTE as 21000, then how is NOTES coded? [2025/56]
(a) 399000
(b) 420000
(c) 440000
(d) 630000
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Ans: (a) 399000
4] If FRANCE is coded as 654321 and GERMANY as 9158437, then how is YEMEN coded? [2025/57]
(a) 54321
(b) 81913
(c) 71913
(d) 71813
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Ans: (d) 71813
5] In a certain code if 64 is written as 343 and 216 is written as 729, then how is 512 written in that code? [2025/66]
(a) 1000
(b) 1331
(c) 1728
(d) 2197
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Ans: (b) 1331
6] If in a certain code, ‘ABCD’ is written as 24 and ‘EFGH’ is written as 1680, then how is IJKL’ written in that code? [2024/77]
(a) 11880
(b) 11240
(c) 7920
(d) 5940
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Ans: (a) 11880
7] If in a certain code, ‘POT’ is written as ATOP and ‘TRAP’ is written as APART, then how is ‘ARENA’ written in that code? [2024/78]
(a) AARENA
(b) AANREA
(c) AANEAR
(d) AANERA
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Ans: (d) AANERA
8] If ‘ZERO’ is written as ‘CHUR, then how is ‘PLAYER’ written? [2023/37]
(a) SOCAGT
(b) SODBGT
(c) SODBHT
(d) SODBHU
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Ans: (d) SODBHU
9] In a code language ‘MATHEMATICS’ is written as ‘LBSIDNZUHDR’. How is CHEMISTRY written in that code language? [2021/56]
(a) DIDLHRSSX
(b) BIDNHTSSX
(c) BIDLHTSSX
(d) DGFLIRUQZ
Show Answer
Ans: (b) BIDNHTSSX
10] The letters from A to Z are numbered from 1 to 26 respectively. If GHI=1578 and DEF=912, then what is ABC =? [2020/48]
(a) 492
(b) 468
(c) 262
(d) 246
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Ans: (d) 246
11] What is the missing term @ in the following? [2020/49]
ACPQ : BESU:: MNGI: @
(a) NPJL
(b) NOJM
(c) NPIL
(d) NPJM
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Ans: (d) NPJM
12] If LSJXVC is the code for MUMBAI, the code for DELHI is [2018/21]
(a) CCIDD
(b) CDKGH
(c) CCJFG
(d) CCIFE
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Ans: (a) CCIDD
13] If RAMON is written as 12345 and DINESH as 675849, then HAMAM will be written as [2018/22]
(a) 92233
(b) 92323
(c) 93322
(d) 93232
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Ans: (b) 92323
14] 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 [2017/60]
(a) 2
(b) 4
(c) 5
(d) 8
Show Answer
Ans: (b) 4
15] A military code writes SYSTEM as SYSMET and NEARER as AENRER. Using the same code, FRACTION can be written as: [2016/61]
(a) CARFTION
(b) FRACNOIT
(c) NOITCARF
(d) CARFNOIT
Show Answer
Ans: (d) CARFNOIT
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