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UPSC CSE CSAT 2022 · Paper II (CSAT) · Question 78 · Number system

The sum of three consecutive integers is equal to their product. How many such possibilities are…

UPSC Civil Services (Preliminary) Examination 2022, General Studies Paper II (CSAT), Question 78 — Number system.

CSAT 2022 · Q78

Number system X-Ray · Core #4 Medium

The sum of three consecutive integers is equal to their product. How many such possibilities are there?

Answer & explanation

Answer: (c) Only three

Writing the integers as n − 1, n, n + 1 gives 3n = n(n² − 1), so n = 0, 2 or −2. That produces three triples: (−1, 0, 1), (1, 2, 3) and (−3, −2, −1).

  1. Let the integers be n − 1, n, n + 1. Sum = 3n; product = n(n² − 1).
  2. 3n = n(n² − 1) gives n = 0 or n² − 1 = 3, i.e. n = 0, 2 or −2.
  3. The triples are (−1, 0, 1), (1, 2, 3) and (−3, −2, −1), with sums 0, 6, −6 equal to their products.
  4. So there are exactly three possibilities. (Testing only positive integers finds just 1, 2, 3.)

Remember · ‘Integers’ includes zero and negatives; solve the algebra instead of testing only positive numbers.

Question and answer: UPSC's official GS Paper II (2022, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). ·

Cite this question: UPSC CSE CSAT 2022, Q78 — minimalistias.com/pyqs/csat/2022/q78

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