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Today Puzzle #598

Puzzle No. 598– Monday 28 October

Lady Margaret Hall, a college of Oxford University, make their first appearance on the student series of University Challenge in the Paxman era tonight. It's a double celebration as Lady Margaret Hall opened their doors 140 years ago in October 1879 as 9 women joined to become among the first women to receive an Oxford education. If all nine women shook hands with each other when they first met, how many different handshakes were there in total?

Today’s #PuzzleForToday has been set by Bobby Seagull, a school Maths teacher and Cambridge University Doctorate student.

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36 handshakes in total. For 9 women in total, the first woman shakes hands with everyone else, that will total 8 handshakes (since they do not shake hands with themselves). The second woman now shakes hands with everyone, except herself and the first woman, with whom she has already shaken hands. This will add 7 handshakes to the total. Continuing along the line, each woman will then add 6, then, 5 and so until the 9th woman, who will already have shaken hands with everyone else, and will add 0 handshakes to the total. The total handshakes is: 8 + 7 + 6 + 5 + 4 + 3 + 2 + 1 = 36

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