Today Puzzle #610
Puzzle No. 610– Wednesday 13 November
Election fever has come to Barchester, as descendants of the characters immortalised by Anthony Trollope compete to be the town’s new MP.
Barchester has 45,000 homes. The three candidates, Brenda Bunce, George Grantly and Harriet Harding, each plan to spend five hours a day for 30 days knocking on voters’ doors. They average one home a minute. What is the percentage chance that any given home will be visited by at least one of the three candidates?
Today’s #PuzzleForToday has been set by Peter Kellner former President of YouGov
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48.8%. Each candidate knocks on 9,000 doors; so 27,000 in total for the three candidates. But some homes will be visited by more than one candidate, so the answer is NOT 27,000 as a percentage of 45,000.
Here’s the route to the answer. Each candidate visits 20% of Barchester’s homes (9,000 as % of 45,000). So each fails to visit 80% of homes. The chance of NOT being visited by ANY of the three candidates is: 80% x 80% x 80% = 51.2%. The number visited by at least one of the candidates is 100-51.2% = 48.8%