Two burning ropes - Brain Teaser

Two burning ropes are needed to measure 45 minutes exactly. Each rope takes exactly one hour to burn, but they don’t burn at a constant rate. Each rope is made of a different material and burns differently from the other. How do we measure 45 minutes exactly by burning both ropes. Check out my other brain teasers if you enjoy this. Two burning ropes - Brain Teaser Bisecting Yin and Yang - Brain Teaser