ESE · 2026 Engineering › Engineering Mathematics & GeneralA deck of n numbered cards is thoroughly shuffled and the cards are inserted into n numbered cells one by one. If the card number i falls in the cell i, we count it as a match, otherwise not, then what is the variance of total number of such matches ?
🔎 The pattern behind this question
This is the same idea UPSC keeps returning to. Start a free trial to see the answer and the full map.
Across examsESE 7 · CAPF 3 · EPFO 2
Evolution“Probability” tested across 7 years (2015–2026)
Study how UPSC repeats — not just the papers
₹199 / 1 year · Founding Member
Full access unlocks the three things no PYQ PDF gives you:
① Cross-exam learning — see the same idea recur across CSE, CAPF, CDS and NDA.
② Topic evolution — how each idea is framed, year by year.
③ Question intelligence — every PYQ + answer, linked to related concepts and similar questions.
e.g. Round Table Conference: CDS 2017 → CSE 2017 → … → CAPF 2024
15 days free, no card required — then ₹199 for 1 year.
Start your 15-day free trial →