Riddle #793


Quick bridge-crossing

Four people come to an old bridge in the middle of the night. The bridge is rickety and can only support 2 people at a time. The people have one flashlight, which needs to be held by any group crossing the bridge because of how dark it is. Each person can cross the bridge at a different rate: one person takes 1 minute, one person takes 2 minutes, one takes 5 minutes, and the one person takes 10 minutes. If two people are crossing the bridge together, it will take both of them the time that it takes the slower person to cross. Unfortunately, there are only 17 minutes worth of batteries left in the flashlight. How can the four travellers cross the bridge before time runs out?
The two keys here are: You want the two slowest people to cross together to consolidate their slow crossing times. You want to make sure the faster people are set up in order to bring the flashlight back quickly after the slow people cross. So the order is: 1-minute and 2-minute cross (2 minute elapsed) 1-minute comes back (3 minutes elapsed) 5-minute and 10-minute cross (13 minutes elapsed) 2-minute comes back (15 minutes elapsed) 1-minute and 2-minute cross (17 minutes elapsed)
89.81 %
41 votes

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If a farmer has 5 haystacks in one field and 4 haystacks in the other field, how many haystacks would he have if he combined them all in the center field?
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Zen Master

A new student met the Zen Master after traveling hundreds of miles by yak cart. He was understandably pleased with himself for being selected to learn at the great master's feet . The first time they formally met, the Zen Master asked, "May I ask you a simple question?" "It would be an honor!" replied the student. "Which is greater, that which has no beginning or that which has no end?" queried the Zen Master. "Come back when you have the answer and can explain why." After the student made many frustrated trips back with answers which the master quickly cast off with a disapproving negative nod, the Zen Master finally said, "Perhaps I should ask you another question?" "Oh, please do!" pleaded the exasperated student. The Zen Master then asked, "Since you do not know that, answer this much simpler riddle. When can a pebble hold back the sea?" Again the student was rebuffed time and again. Several more questions followed with the same result. Each time, the student could not find the correct answer. Finally, completely exasperated, the student began to weep, "Master, I am a complete idiot. I can not solve even the simplest riddle from you!" Suddenly, the student stopped, sat down, and said, "I am ready for my second lesson." What was the Zen Master's first lesson?
The student's first lesson was that in order to learn from the Zen Master, the student should be asking the questions and not the Zen Master.
88.20 %
48 votes


Course of expensive medication

You've been placed on a course of expensive medication in which you are to take one tablet of Sildenafil and one tablet of Citrate daily. You must be careful that you take just one of each because taking more of either can have serious side effects. Taking Sildenafil without taking Citrate, or vice versa, can also be very serious, because they must be taken together in order to be effective. In summary, you must take exactly one of the Sildenafil pills and one of the Citrate pills at one time. Therefore, you open up the Sildenafil bottle, and you tap one Sildenafil pill into your hand. You put that bottle aside and you open the Citrate bottle. You do the same, but by mistake, two Citrates fall into your hand with the Sildenafil pill. Now, here's the problem. You weren't watching your hand as the pills fell into it, so you can't tell the Sildenafil pill apart from the two Citrate pills. The pills look identical. They are both the same size, same weight (10 micrograms), same color (Blue), same shape (perfect square), same everything, and they are not marked differently in any way. What are you going to do? You cannot tell which pill is which, and they cost $300 a piece, so you cannot afford to throw them away and start over again. How do you get your daily dose of exactly one Sildenafil and exactly one Citrate without wasting any of the pills?
Carefully cut each of the three pills in half, and carefully separate them into two piles, with half of each pill in each pile. You do not know which pill is which, but you are 100% sure that each of the two piles now contains two halves of Cirate and half of Sildenafil. Now go back into the Sildenafil bottle, take out a pill, cut it in half, and add one half to each stack. Now you have two stacks, each one containing two halves of Sildenafil and two halves of Citrate. Take one stack of pills today, and save the second stack for tomorrow.
83.96 %
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Maths magic riddle

Tarun Asthnaiya go to his office by local train. However nearby train station is quite far from his place and he used to drive his bike to train station daily with an average speed of 60km/hr. One day at halfway point he relized that due to heavy traffic he got late having average speed of just 30km/hr. How fast he must drive for the rest of the way to catch my local train?
The train is just about to leave the station and there is no way Tarun will be able to catch it this time.
85.32 %
38 votes


The bamboo pole

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Jamie died of carbon dioxide poisoning. The pole was 5' long, but only the size of a quarter. The first time he breathed in, he breathed oxygen. When he exhaled, the air could not travel 5' before he breathed in again. He was just breathing what he exhaled. Before long, all he was breathing was carbon dioxide. He died of CO2 poisoning. Doctor Doge was the one who told him to use the pole, therefore the cause of his death. Dodge is a DOCTOR, and therefore knows about the CO2. Dodge did murder Jamie. His motive: the money in the will.
62.71 %
164 votes


Twin brother

Peter celebrated his birthday on one day, and two days later his older twin brother, Paul, celebrated his birthday. How could this be?
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89.33 %
39 votes



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85.67 %
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82.37 %
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A quarter and a dime. One coin is not a dime, but the other one is.
85.67 %
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