Good Riddles

Answer: Both ends are nailed with the same nail. In order for the 10 foot chain to dip down 5 feet it must dip 5 feet down and 5 feet up, totaling the length of the chain.

Answer: Tip the glass of water until the water reaches the rim of the glass and if the water lines up perfectly with the bottom rim of the glass, it is half full.

Answer: A piece of fruit would be taken from the "Apples and oranges" box. Since this is the wrong label you know whatever fruit you draw from this box is all the same and you can give that box the proper label. Since all of the boxes started out wrong you know that the last box with its original label is wrong and can be labeled "Apples and oranges". From here you can just put the final label on the final box.

Answer: 22 times: 12:00:00, 1:05:27, 2:10:55, 3:16:22, 4:21:49, 5:27:16, 6:32:44, 7:38:11, 8:43:38, 9:49:05, 10:54:33. Each twice a day.

Answer: Start both hourglasses then when the 11 minute hourglass has finished immediately flip it again. When the 13 minute hourglass runs out the 11 minute hourglass will have 9 minutes left, so flip it and it will last another 2 minutes, 13 minutes + 2 minutes = 15 minutes.