there are two ropes and each can burn upto 1 hour. Or you can say that they will be completely burned out in one hour each. Then how you can calculate 45 minutes.

• consider two ropes one as A and the other one as B . now set the fire on both the ends of rope A and at one end of rope B , It will take 30 minutes to burn rope A and half of the rope B will be burnt now set fire at the other end of rope B, it will take 15 minutes to burn rope B . so totally it takes 30+15=45 minutes
• 7 years agoHelpfull: Yes(1) No(0)
• Take both ropes as A and B respectively. Light the rope A at both ends and rope B at one end. After 30 mins rope A is all burnt and rope B is half way. Now repeat the same by lighting rope B at both ends which gets completed by 15 mins. So finally 30 + 15 = 45 mins using two ropes.
• 6 years agoHelpfull: Yes(0) No(0)