How to Increase IQ
Brain Exercises

Benefits of Meditation
Mental Math

Be a Deep Thinker
Lateral Thinking

More Free Riddles

Here are some more free riddles. To start with, there is the following lateral thinking puzzle I recently dreamt up. Have fun!

The Jail Cell Clock

You are locked in a jail cell with no windows. and you need to tap out a message on the wall for the man in the other cell next to you. The problem is that you have to do it at exactly 9:15 PM, when the guard outside is switched, so your noise won't be noticed. You can't hear the switching of the guards through your walls, and you have no clock.

There is a faucet with water dripping very consistently from it in the corner, but you don't know if it is dripping at 30 or 40 or however many drops per minute, and that wouldn't give you the time in any case. You can just make out the chiming of a church bell, but it chimes just once at the top of each hour, so you can't tell the time from that. You can feel the wall facing west start to cool after the sun sets, but you don't know what time the sun is setting, and this isn't very precise in any case. Your dinner is always passed into your cell between 6:15 and 6:45. How do you determine when it is exactly 9:15 PM?

How Many Seconds?

If a clock takes six seconds to strike six times at six o'clock, how many seconds will it take to strike eleven times at eleven o'clock?

Another Clock Riddle

On May 5, 2006, three clocks were set at noon. The following day at noon, one was found to be a minute slow, another a minute fast, and the third still had the exact time. If they continue at the same speeds, on what date will they once again all read 12:00?

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Answers to the Riddles

The Jail Cell Clock

After dinner arrives, you listen for the church bell. Since dinner comes between 6:15 and 6:45, the next chiming has to be at 7:00 PM. When you hear it, you start to count the drips from the faucet until you hear the chime again at 8:00 PM. Divide the number of drips by four, and you'll have the number of drips that fall in fifteen minutes (Or you can divide by sixty to get the drops per minute, and then multiply this by fifteen). When the bell chimes again at 9:00, you start counting drips until you reach the specified number. It is now 9:15 PM, and time to tap out your message.

How Many Seconds?

12 seconds. The timing would naturally start on the first strike. At six, there would be five more strikes in the next six seconds, for a time of 1.2 seconds per strike. After the first strike at eleven, the following ten strikes would then take 12 seconds.

Another Clock Riddle

One must lose twelve hours and the other gain twelve to read the same as the correct one. Twelve hours is 720 minutes, so it will take 720 days from the first day to all be synchronized at 12:00 again. This would be on April 24, 2008 (2008 is a leap year).


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