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Question

A group of 20 students are sitting in a circle. Each shakes hands with exactly 3 neighbours. How many handshakes occur?

This question was previously asked in
SSC CGL 2025 Tier 2 Paper 1 Question Paper (19-Jan-2026)
The correct answer is

30

If every one of the \(n = 20\) students shakes hands with exactly \(d = 3\) others, then the sum of degrees is \(n \times d = 20 \times 3 = 60\).

Each handshake is counted twice in the degree sum (once for each participant), so the number of distinct handshakes is

\(\dfrac{n \times d}{2} = \dfrac{60}{2} = 30\).

Hence the correct answer is 30.

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