For the puzzle regarding the thread, take the first thread and burn it on both ends and only one end of the second thread at the same time. This way when the first thread burns out it will be 30 minutes. Then after as soon as the first thread burns out then light the other end of the second thread as well (which would have been half burnt by now). Then the remaining part of the thread should burn out in 15 minutes. Hence you get 30 + 15 = 45 minutes. Thank you.