Are you a Da vinci type?

If you have two lengths of string, which although they are not the same length, will each take exactly 30 minutes for a flame to burn from one end of the string to the other. The strings do not burn evenly, so the position of a flame, as it burns through a string, will not afford you any specific knowledge of how much time the string has been burning for. All you know is that it takes exactly 30 minutes for a flame to burn from one end of each string to the other end. How can you use these two strings and matches to measure out exactly 45 minutes with almost perfect accuracy?



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