Enigma 1567: My round
21 February 2012
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From New Scientist #2730, 17th October 2009 [link]
A group of friends and I each had a half-pint of shandy (beer mixed with lemonade), but the proportion of lemonade to beer varied from glass to glass. Overall, I had a certain whole-number percentage of the lemonade used in the round of drinks, and a certain whole-number percentage of the beer. The percentage of beer was 5 more than that of the lemonade.
If I now told you the actual percentages it would be possible to work out how many of us there were in the group.
Knowing that, if instead I now told you how many of us there were, you could work out the percentages.
How many of us were there, and what percentage of the lemonade did I have?