mattgadient.com » Riddles, Puzzles, Brain Teasers

Rub a dub dub, 3 men in a tub (actually a boat).

Matthew Gadient — Wed, 11 Oct 2006 10:56:30 +0000

Let’s get right down to the problem… You have 3 people who are on an island. We’ll call them Mark, Ryan, and Evan. Unfortunately, they have to leave. Maybe they’ve run out of food, maybe the island is burning down, or maybe they just need a change of scenery. We don’t know why, and it doesn’t matter. The point is, they need to travel to another island which is miles and miles away. The good news is that they have a boat. Their boat can hold up to 200 pounds in weight. This creates a problem though because:

Mark is 100 pounds
Ryan is 100 pounds
Evan is 200 pounds

Obviously, they cannot go all at once, or the boat will sink. This means the boat’s going to have to make more than 1 trip. So the question is… how do they all get to the other island?

Scroll down for the answer.

Tip: Draw it out on a piece of paper.

Tip: The boat will make a total of 5 trips (3 of them to the new island, and 2 of them back to the old one)

Answer:
Mark and Ryan take the boat to the new island. Mark drops off Ryan, and then Mark takes the boat back to the old island. Mark gets off at the old island, while Evan takes the boat to the new island. Evan gets off at the new island. Ryan gets back on and goes to the old island, picks up Mark, and then Ryan and Mark travel to the new island.

Why can’t you connect neutral to ground to convert an outlet from 2-prong to 3-prong?

Matthew Gadient — Thu, 06 Apr 2006 08:26:28 +0000

Not everything I put in the riddles, puzzles, and brain teasers section involves a king and some sort of puzzle that has to be solved with fancy logic. Sometimes it’s a real life question, and this is one of those times.

The question of course is if you have a 2-prong outlet (live + neutral) and want to convert it to a 3-prong (live + neutral + ground), why can’t you simply use a little jumper-wire on the new outlet and hook up ground to neutral? After all, they both go to ground eventually. This would mean that your surge protector that needs ground to operate correctly would work (surge protectors simply dump surges to ground before they hit your equipment). The problem is, by connecting neutral to ground in the outlet, there’s a situation that could happen that could kill you. No, it doesn’t have to do with the surge protector or power surges. Want to guess what it is?

Answer

If the neutral wire in the walls were ever to become disconnected/broken/etc, any 3-prong devices that were connected to the outlet (for example, a computer) would now have a live case. If you touched the case, you could be electrocuted.

You see, the metal case on 3-prong devices is always connected to the ground prong, mainly because if there were a problem in the device and the case somehow became live, that power would have a clean path to ground and would hopefully blow a circuit breaker before any harm could be done.

Since you connected the neutral prong directly to the ground prong, the case itself now has the potential to carry the return current. If the neutral connection were ever broken, it would, and if you touched the case (and were yourself grounded), your body would be completing the circuit. The device might even power on for as long as you were touching it. Unfortunately, all that current would be running through your body. For those of you who have seen the “call before you dig” commercials, you’ve probably got an idea of what would happen next… Never a good thing.

Note for those who haven’t seen the “call before you dig” commercials…

You die.

The Four Wise-men, the Angry King, and the Hats.

Matthew Gadient — Tue, 04 Apr 2006 21:59:31 +0000

Once upon a time, there was a powerful kingdom with a powerful king. Like so many other kings, this king had a lust for popularity, a lust for power, and a lust to be loved by all. Unfortunately for the king, his people did not look up to him. Rather, in times of need, they looked to the 4 wise men who lived in his lands, as they were very wise, and very kind, and had the answers to all problems. It was generally accepted that the wise men were smarter than the king, and this bothered the king greatly.

In most cases, the king could simply order that they be put to death. However, he knew that this would greatly upset the people. He decided to come up with a plan to outsmart the wise men, proving that they were not as wise as the people believed. After embarrassing them publically with a problem they could not solve, he knew the people would more readily accept his decision to end their lives.

The king ordered stands to be built in his courtyard, as well as a solid brick wall. He then called for the wise men and had them placed in the following positions. They each of course knew their position:

The king then said the following:

You are here today because you claim to be the wisest of all men, but I am going to prove you wrong with a test. You will each be blindfolded shortly. While you are blindfolded, a hat will be placed upon each of your heads. There are exactly 2 red hats and 2 green hats. Once the hats are on your heads, the blindfold will be removed. You will not be able to see the color of the hat on your own head, nor will you be able to see the color of the hat on the person behind you. You must face forward at all times and may not move or turn. To make this even more difficult, one of you will be separated by a brick wall so that you can not see the others and they can not see you. You may not speak or communicate in any way, except to answer my question….

The king then had the hats put on them in this way:

He said the following:

The question that any one of you must answer is “what color hat do you have on?”. Only one of you may answer. If you answer correctly, you all live. If you answer incorrectly, you all die. Remember, you may not speak, move, or otherwise communicate except to answer my question. Also remember that there are exactly 2 green hats and exactly 2 red hats. Take all the time you need.

As it turns out, after a short time, one of the wise men answered. He was of course certain of his answer, and was correct. The king, baffled at the incredible intelligence was forced to let them all go. Now your questions are as follows:

Who answered?
How did they know the color of their hat?

THE ANSWER IS BELOW

Tip #1: Think about what they can each see.

Answer to Tip #1: Wise man #1 can’t see anything. Neither can #2. Wise man #3 can see the person in front of him, and Wise man #4 can see both of the people in front of him.

Tip #2: If they were each to *guess* based on the odds, what would each of them guess?

Answer to Tip #2: Wise man #1 and #2 cannot see anything at all, so they have a 50% chance of being either green or red. Wise man #3 sees a green hat in front of him. He therefore knows that there is 1 green hat left, and 2 red hats left. Based on those odds, there’s a 66% chance that he is red. Wise man #4 sees both a green hat and a red hat in front of him. Since there is 1 green hat and 1 red hat left, his chances are being either are 50%.

Tip #3: PART OF THE ANSWER: Wise man #3 is the one who answers. In this case, he says “RED”. Of course, he is correct. No, he wasn’t guessing. So how did he know?

Tip #4: Remember, he didn’t answer right away. It says that “after a short time, one of them answered”. Why didn’t he answer right away?

Tip #5: Only Wise man #3 and #4 could see anything. What are the possible combinations based upon what they can see?

ANSWER:

The one thing that Wise man #3 and #4 have in common is that they both see that Wise man #2 is green. After waiting a short time, Wise man #3 knows that he can not be green. If he were, this would be the only possible combination (with 2 red hats and 2 green hats):

If that were the case, Wise man #4 would have seen 2 green hats, and since there are ONLY 2 green hats, Wise man #4 would have answered RED. Basically, if #2 and #3 were the same color, #4 would answer the opposite color.

Because #4 did not answer, #3 knew that he had to be the opposite color of #2, so he was able to confidently answer correctly.