This question already has an answer here:
- The Dragon or the Magnifying Glass? 4 answers
A man is trapped in a room with only two exits. One exit leads into a room made of magnifying glass and instantly fries anything going into it in the hot summer sun. The other door, leads into a room with a fire breathing dragon inside. How does he escape?
I give credit for this riddle to Riddle.fyi
Sorry. I did not realise this was a duplicate.