Answer to brain teaser #17
The answer is (A). Since it must happen, the probability is actually 1 (100%).
Explanation: Firstly, consider 2 men, one starting from the top of the mountain and hiking down while the other starts at the bottom and hikes up. At some time in the day, they will cross over. In other words they will be at the same place at the same time of day.
Now consider our man who has walked up on one day and begins the descent the next day. Imagine there is someone (a second person) shadowing his exact movements from the day before. When he meets his shadower (it must happen) it will be the exact place that he was the day before, and of course they are both at this spot at the same time.
Contrary to our common sense, which seems to say that this is an extremely unlikely event, it is a certainty.
NOTE: There is one unlikely event here, and that is that he will notice the time when he is at the correct location on both days, but that was not what the question asked.
Brain teaser#18
A part of the body is hidden in each of the following sentences. The first sentence contains "head." Can you find the rest?
1. The ad is for Monday's sale.
2. The tour group can go to either country.
3. My car makes funny noises sometimes.
4. Sarah and Tony are getting married.
5. That casino seems shady.
6. Can't you see that Hank needs help?
7. The sea is so calm out here.
8. Would you like to go surfing, Erin?
Wednesday, July 18, 2007
Wednesday, July 4, 2007
Answer to brain teaser #16, brain teaser #17
Answer to brain teaser #16
The judge then said, "Merchant, you stated that the purse you lost contained 200 pieces of gold. Well, that's a considerable loss, but the purse this beggar found had only 100 pieces of gold. Therefore, it couldn't be the one you lost." With that, the judge gave the purse with 100 pieces of gold to the beggar, and told the merchant that he did not have to pay a reward.
There might just be a leather bag out there somewhere still with 200 pieces of gold in it, but don't ask the merchant, the beggar, or me.
Brain teaser #17
A hiker climbs all day up a steep mountain path and arrives at the mountain top where he camps overnight. The next day he begins the descent down the same trail to the bottom of the mountain when suddenly he looks at his watch and exclaims, "That is amazing! I was at this very same spot at exactly the same time of day yesterday on my way up."
What is the probability that a hiker will be at exactly the same spot on the mountain at the same time of day on his return trip, as he was on the previous day's hike up the mountain?
Is the probability closest to (A) 99% or (B) 50% or (C) 0.1% ?
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