Puzzle: You have 2 identical ropes with same shape and size. One rope takes 1 hour to burn completely. How you will measure 45 minutes.
Note: you are not allowed to cut or fold these ropes.
Solution: Suppose these two ropes are A and B respectively. Now we will sat on fire rope A with the both ends and rope B from one end. Now when rope A burnt completely it means 30 minutes has been passed, so now sat on fire rope B from another end. That’s how it will burn completely in next 15 minutes. By this we can calculate 45 minutes.