Let each fuse burn for 15 minutes and extinguish them. The rest of each fuse will burn for 45 minutes.

>You have two fuses of variable lengths.
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>Each fuse burns for exactly 1 hour.
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>Each fuse burns unevenly. ( example 1/10th of the fuse could burn for 50 minutes and the rest of the fuse could take 10 minutes. ) You don't know until after the fuse has burned up.
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>Make the two fuses last exactly 45 minutes.