Roping in time!!

You have two ropes. Each takes exactly 60 minutes to burn. They are made of different material so even though they take the same amount of time to burn, they burn at separate rates. In addition, each rope burns inconsistently. How do you measure out exactly 45 minutes?

Answer:
Take one rope and burn both ends of it at both ends. At the same time, burn one side of the other rope. When the first rope burns out, burn the other side of the second rope as well. When it burns out completely, the time is 45 minutes.