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CSAT · 113 questions

Puzzles, arrangements & general mental ability

Every UPSC CSAT question on this topic, 2016–2026, newest first. Tap an option to check yourself; the answer and explanation open below it.

Puzzles, arrangements & general mental ability questions per year: 2016: 19, 2017: 18, 2018: 17, 2019: 10, 2020: 3, 2021: 10, 2022: 5, 2023: 7, 2024: 8, 2025: 8, 2026: 8 Asked in 11 of 11 years · most in 2016 (19)

UPSC syllabus: “General mental ability;” See the full syllabus →

CSAT 2020 · Q20

Medium

If in a particular year 12th January is a Sunday, then which one of the following is correct?

Answer & explanation

Answer: (c) 12th July is a Sunday if the year is a leap year.

From 12 January to 12 July is 181 days in an ordinary year and 182 days in a leap year. 182 is exactly 26 weeks, so in a leap year 12 July falls on the same day, Sunday.

  1. Days from 12 January to 12 July: January 31, February 28 or 29, March 31, April 30, May 31, June 30.
  2. Ordinary year: 181 days = 25 weeks + 6 days, so 12 July is Saturday.
  3. Leap year: 182 days = 26 weeks exactly, so 12 July is Sunday.
  4. 15 July is then Tuesday (ordinary year) or Wednesday (leap year), never Sunday — (a), (b) and (d) fail.

Remember · Count days between the two dates and divide by 7; the remainder is the number of weekdays to move forward.

Question and answer: UPSC's official GS Paper II (2020, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink ·

CSAT 2020 · Q34

Easy

Consider the following sequence of numbers:

5 1 4 7 3 9 8 5 7 2 6 3 1 5 8 6 3 8 5 2 2 4 3 4 9 6

How many odd numbers are followed by the odd number in the above sequence?

Answer & explanation

Answer: (b) 6

Scan the 26 digits once and mark every place where an odd digit is immediately followed by another odd digit. There are six such places: 5-1, 7-3, 3-9, 5-7, 3-1 and 1-5.

  1. Pairs in order: 5-1 ✓, 1-4, 4-7, 7-3 ✓, 3-9 ✓, 9-8, 8-5, 5-7 ✓, 7-2, 2-6, 6-3, 3-1 ✓, 1-5 ✓, 5-8 …
  2. After 5-8 the odd digits are 3, 5, 3 and 9, and each is followed by an even digit (8, 2, 4, 6).
  3. Total odd-odd pairs = 6.

Remember · For adjacency counts, scan pairs left to right in one pass and tick each hit; do not restart counting.

Question and answer: UPSC's official GS Paper II (2020, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink ·

CSAT 2020 · Q35

Medium

A is 16th from the left end in a row of boys and V is 18th from the right end. G is 11th from A towards the right and 3rd from V towards the right end. How many boys are there in the row?

Answer & explanation

Answer: (b) 41

G is 11 places to the right of A, so G is 27th from the left. G is also 3 places to the right of V, so V is 24th from the left. V is 18th from the right, so the row has 24 + 18 − 1 = 41 boys.

  1. A is 16th from the left; G is 11th to A's right, so G is 16 + 11 = 27th from the left.
  2. G is 3rd to V's right, so V is 27 − 3 = 24th from the left.
  3. V is 18th from the right, so total = 24 + 18 − 1 = 41.
  4. Check: G is then 41 − 27 + 1 = 15th from the right, which is 3 places right of V (18th).

Remember · Convert every position to one end, then total = position from left + position from right − 1.

Question and answer: UPSC's official GS Paper II (2020, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink ·

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