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Riddle:

Express 100 with 5 1s. Express 100 three ways with five 5s. You can use brackets, parentheses and these signs +,-,X, /

 

Answer:

111-11=100

(5 x 5 x 5)-(5 x 5)=100; (5+5+5+5)x 5=100;(5 x 5)(5-(5/5)=100.

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Riddle:

An alarm clock runs 4 minutes slow every hour. It was set right 3 1/2 hours ago. Now another clock which is correct shows noon. 

In how many minutes, to the nearest minutes, to the nearest minute, will the alarm clock show noon?

Answer:

In 3 1/2 hours the alarm clock has become 14 minutes slow. At noon the alarm clock will fall behind approximently an additional minute. Its hands will show noon in 15 minutes.

 

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Riddle:

You want to send a valuable object to a friend. You have a box which is more than large enough to contain the object. You have several locks with keys. The box has a locking ring which is more than large enough to have a lock attached. But your friend does not have the key to any lock that you have. How do you do it? Note that you cannot send a key in an unlocked box, since it might be copied.

Answer:

Attach a lock to the ring. Send it to her. She attaches her own lock and sends it back. You remove your lock and send it back to her. She removes her lock.

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Riddle:

My first is a creature whose breeding is unclear. My second, a price you must pay. My whole can be found in the river of Time and refers to events of today. What am I?

Answer:

Current.

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Riddle:

If you like pretty gems that sparkle and shine, I invite you to dig in my virtual mine. My first is purple, fit for a king, My second is green where Dorothy did her thing. My third is red, July's birthstone as well, My fourth is seen in strings and is found inside a shell. My fifth is hard, pure Carbon and expensive to buy, My sixth is Crocodolite, striped like the big cat's eye. Seventh is two words, a man-made fake of April's stone, Eighth is very dark and found at Lightning Ridge alone. Now take from each gem, one letter in its turn, And you will find the stuff for which even the god's yearn.

Answer:

Answer: Ambrosia The gems are: Amethyst Emerald ( Emerald City in the Wizard of Oz ) Ruby Pearl Diamond Tiger's eye Cubic Zirconium (Fake diamond) Black Opal Taking the first letter of Amethyst, second of Emerald, etc.. gives Ambrosia - The food of the gods.

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Riddle:

How many cats are in a small room if in each of the four corners a cat is sitting, and opposite each cat there sit three cats, and a each cat's tail another is sitting?

Answer:

Four cats, each near a tail of a cat in an adjacent corner.

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Riddle:

A boy presses a side of a blue pencil to a side of a yellow pencil, holding both pencils vertically. One inch of the pressed side of the blue pencil, measuring from its lower end, is smeared with paint. The yellow pencil is held steady while the boy slides the blue pencil down 1 inch, continueing to press it against the yellow one. He returns the blue pencil to its former position, then again it slides down 1 inch. He continues until he has lowered the blue pencil 5 times and raised it 5 times- 10 moves in all.

Supposed that during this time the paint neither dries nor diminishes in quantity. How many inches of each pencil will be sneared with paint after the tenth move?

 

Answer:

At the start, 1inch of the yellow pencil gets smeared with wet paint. As the blue pencil is moved downward, a second inch of the blue pencils smears a second inch of the yellow pencil.

Each pair of down and up movesof the blue pencil smears 1 more inch of each pencil. 5 pairs of moves will smear 5 inches. This together with the initial inch, makes 6 inches for each pencil.

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Riddle:

An item is made from lead blanks in a lathe shop. Each blank suffices for 1 item. Lead shavings accumulated for making 6 items can be melted and made into a blank. How many items can be made from 36 blanks.

Answer:

From 36 blanks there are 36 items made. The lead shavings are enough to make 6 blanks. Which make 6 more items. But don't stop here. The new shavings are good for 1 more item. Total: 43

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Riddle:

When the celebrated German mathematician Karl Friedrich Gauss (1777-1855) was nine he was asked to add all the integers from 1 through 100. He quickly added 1 to 100, 2 to 99, and so on for 50 pairs of numbers each adding to 101.

Answer: 50 X 101=5,050.

Now find the sum of all the digits in integers from 1 through 1,000,000,000.

That's all the digits in all the numbers, not all the numbers themselves.

Answer:

The numbers can be grouped by pairs:

999,999,999 and 0;

999,999,998 and 1'

999,999,997 and 2;

and so on....

There are half a billion pairs, and the sum of the digits in each pair is 81. The digits in the unpaired number, 1,000,000,000, add to 1. Then:

(500,000,000 X 81) + 1= 40,500,000,001.

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Riddle:

A soccer fan, upset by the defeat of his favorite team, slept restlessly. In his dream a goalkeeper was practicing in a large unfurnished room, tossing a soccer ball against the wall and then catching it.

But the goalkeeper grew smaller and smaller and then changed into a ping-pong ball while the soccer ball was swelled up into a huge cast-iron ball. The iron ball circled round madly, trying to crush the ping-pong ball, how did the ping-pong find safety whithout leaving the floor?

Answer:

If the ping-pong ball rolls flush against the wall, the cast-iron ball cannot crush it.

Those who know geometry can determine that if the diameter of a large ball is at least 5.83 (3+2(square root of 2) times as large as the diameter of a little ball, then the little ball will be safe if it hugs the wall.

A cast-iron ball that is larger than a soccer ball is more than 4.83 times as large in diameter as a ping-pong ball.

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