1. One of the classic puzzles that can confuse anyone. The solution is that you dont add the bellboys $2 to the $27, you subtract it. They paid $27, the bellboy kept $2, and $25 was for the room.
2. Actually this is not a very clever question. There could be multiple solutions and i suppose that we have to specify both the solutions because the author can think in different ways.
Solution 1: 45 minutes? The first man can do three in 45 minutes whilst the other would take 25 mins to do one.
Solution 2: In 150 mins the first man can assemble 10 computers and the second man 6. Therefore, 16 computers in 150 mins quartered is 4 computers in 37.5 mins. This assumes that they can work together on the same computer at their same individual rate.
3. Light both ends of the 10 minute fuse at once. When those burning ends meet somewhere in the middle, light the 15 minute fuse. When that is finished burning, 20 minutes are up.
4. This is difficult for people and you are unlucky to get it without having read this once before. Take 1 piece from the 1st bag, 2 pieces from the 2nd bag, 3 from third bag and so on up to 9 pieces from the 9th bag. The total weight W would normally be 45. If it is, the 10th bag has the lighter pieces. Otherwise the number of the guilty bag is (45 - W) x 10.
5. Another classic problem. Start with all switches off. Turn switch A on and wait around 5 minutes. Turn A off and B on. Go into the room. Light bulb connected to switch A is off and hot, B is on, and C is off and cold.
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