- #1
Harmony
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Question:
Must every year have at least one Friday which is on the 13th?
By listing out all the dates, I found that for any year, day 1st-7th must appear at least once for the the first Friday of the months. Hence, there must be at least a month which the first Friday is on the 6th. Thus, I deduce that every year must have at least one Friday which is on the 13th.
But how do I prove it mathematically? Does the dates form sequence? Is calculus needed for this question?
Must every year have at least one Friday which is on the 13th?
By listing out all the dates, I found that for any year, day 1st-7th must appear at least once for the the first Friday of the months. Hence, there must be at least a month which the first Friday is on the 6th. Thus, I deduce that every year must have at least one Friday which is on the 13th.
But how do I prove it mathematically? Does the dates form sequence? Is calculus needed for this question?