Got this one here at Sharp Brains. It is called party for polyglots written by Wes Carrol. Enjoy.
'Of the 100 people at a recent party, 90 spoke Spanish, 80 spoke Italian, and 75 spoke Mandarin. At least how many spoke all three languages?'
Answer below:
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Hopefully this useless text that I am now writing is enough to keep your peripheral vision from accidentally picking up the answer. The answer is 45. The explanation is '10 could not speak Spanish, 20 could not speak Italian, and 25 could not speak Mandarin. So there could have been 10 people who spoke none of those languages.
However, that would maximize the number of people who could speak all three, and the problem asks at least how many speak all three. Therefore, we must assume that these 10, 20, and 25 people are all separate people. Having identified 55 each of whom is missing one language, the remaining 45 speak all three.
