show that at least 3 of any 25 days chosen must fall in the same month of the year.please halp!

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==> In order to figure this out, you have to know that there are 12 months in the year.Take a calendar.  You have to pick 25 days in it.First 12 days you pick:You want to avoid bunching them up, so you pick each one from a different month.Next 12 days you pick:You want to avoid bunching them up, so you pick each of these from a different month too.So far, you've picked (12 + 12) = 24 numbers, and there are two from each month.Last day you pick:You still have to pick one more number to make 25.What month will you pick it from ?WHATEVER month you pick it from, you'll have three days from that month.