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"Any" Riddles - Next 10 of 557.

Riddle: Twelve flags stand equidistant along the track at the stadium. The runners start at the first flag. A runner reaches the eighth flag 8 seconds after he starts. If he runs at an even speed, how many seconds does he need altogether to reach the twelfth flag?
Answer: Not 12 seconds. There are 7 segments from the first flag tot the eighth, and 11 from the first to the twelfth. He runs each segment in 8/7 seconds; therefore, 11 segments take 88/7= 12 4/7 seconds.
Riddle: A hundred stones are placed, in a straight line, a yard distant from each other. How many yards must a person walk, who undertakes to pick them up, and place them in a basket stationed one yard from the first stone?
Answer: In solving this question it is clear that to pick up the first stone and put it into the basket, the person must walk two yards, one in going for the stone and another in returning with it; that for the second stone he must walk four yards, and so on increasing by two as far as the hundredth, when he must walk two hundred yards, so that the sum total will be the product of 202 multiplied by 50, or 10,100 yards. If any one does not see why we multiply 202 by 50 in getting the answer, we refer him to his arithmetic.
Riddle: Lazy Larry agreed to work on a job for his brother-in-law for thirty hours at eight dollars an hour, on the condition that he would forfeit ten dollars per hour for every hour that he idled. At the end of the thirty hours Larry wasn't owed any money and didn't owe his brother-in-law any money either. How many hours did Larry work and how many hours did he idle?
Answer: Lazy Larry worked 16-2/3 hours and idled 13-1/3 hours. 16-2/3 hours, at $8.00 an hour amounts to the same amount as 13-1/3 hours at $10.00 per hour.
Riddle: I like to be blue and have been since '63, but I could be anything if my circuit was fixed. I'm small yet infinitely bigger. I was grown but I'm made of metal. I am the last of my kind just like my beautiful idiot once was. Together we will travel, have traveled or are traveling. Tenses as seen, seeing, will see, are mysterious to me. Wibblies and wobblies, time correctly described by a Lord. What will I be, what have I been, or is it, what am I?
Answer: The T.A.R.D.I.S. from Doctor Who.
Riddle: You're stranded in a rainforest, and you've eaten a poisonous mushroom. To save your life, you need an antidote excreted by a certain species of frog. Unfortunately, only the female frog produces the antidote. The male and female look identical, but the male frog has a distinctive croak. Derek Abbott shows how to use conditional probability to make sure you lick the right frog and get out alive. How do you get out alive?
Answer: If you chose to go to the clearing, you're right, but the hard part is correctly calculating your odds.  There are two common incorrect ways of solving this problem.  Wrong answer number one:  Assuming there's a roughly equal number of males and females, the probability of any one frog being either sex is one in two, which is 0.5, or 50%.  And since all frogs are independent of each other, the chance of any one of them being female should still be 50% each time you choose.  This logic actually is correct for the tree stump, but not for the clearing.  Wrong answer two:  First, you saw two frogs in the clearing.  Now you've learned that at least one of them is male, but what are the chances that both are?  If the probability of each individual frog being male is 0.5, then multiplying the two together will give you 0.25, which is one in four, or 25%.  So, you have a 75% chance of getting at least one female and receiving the antidote.  So here's the right answer.  Going for the clearing gives you a two in three chance of survival, or about 67%.  If you're wondering how this could possibly be right, it's because of something called conditional probability.  Let's see how it unfolds.  When we first see the two frogs, there are several possible combinations of male and female. If we write out the full list, we have what mathematicians call the sample space, and as we can see, out of the four possible combinations, only one has two males.  So why was the answer of 75% wrong?  Because the croak gives us additional information.  As soon as we know that one of the frogs is male, that tells us there can't be a pair of females, which means we can eliminate that possibility from the sample space, leaving us with three possible combinations.  Of them, one still has two males, giving us our two in three, or 67% chance of getting a female.  This is how conditional probability works.  You start off with a large sample space that includes every possibility.  But every additional piece of information allows you to eliminate possibilities, shrinking the sample space and increasing the probability of getting a particular combination.  The point is that information affects probability.  And conditional probability isn't just the stuff of abstract mathematical games. It pops up in the real world, as well.  Computers and other devices use conditional probability to detect likely errors in the strings of 1's and 0's that all our data consists of.  And in many of our own life decisions, we use information gained from past experience and our surroundings to narrow down our choices to the best options so that maybe next time, we can avoid eating that poisonous mushroom in the first place.
Riddle: An officer wishing to arrange his men in a solid square found by his first arrangement that he had 39 men left over. He then started increasing the number of men on a side by one, but found that 50 additional men would be needed to complete a new square. How many men did the officer have?
Answer: The officer had 1975 men. When he formed a square measuring 44 by 44, he had 39 men over. When he tried to form a square 45 x 45, he was 50 men short.
Riddle: A house has 6 stories, each the same height. How many times as long is the ascent to the sixth floor as the ascent to the third?
Answer: 2 1/2 times (5/2, not 6/3).
Riddle: Lauren and Alice are talking long distance on the phone. Lauren is in an East-Coast US state which borders the Atlantic Ocean, and Alice is in a West-Coast state which borders the Pacific Ocean. Lauren asks Alice: "What time is it?" Alice replies and Lauren says: "That's really odd. It's the same time here!" How can this be?
Answer: Alice is in Eastern Oregon (in Mountain time) and Lauren is in Western Florida (in Central time). It is the night that daylight-savings time changes back to standard time any time after 1:00 and before 2:00 AM.
Riddle: How many three cent stamps are in a dozen?
Answer: A dozen, although you probably said four.
Riddle: There is a certain family with both girl and boy children. Each of the boys has the same number of brothers as he has sisters. Each of the girls has twice as many brothers as she has sisters. How many boys and girls are there in this family?
Answer: Four boys and three girls.