Brain Teaser Puzzles

Try your hand at solving our fun brain teaser puzzles.

Find the Security Code - Brain Teaser

Jerilee had a new toy - a random number generator. When she ran it, she noticed something interesting in the first ten numbers. When she compared the ten numbers to the security code on her house alarm, each one had exactly one digit, in the proper placement, as the security code.

The first number was 14073. For this number, the security code could not be 34170 because two digits would be correctly placed, or 92365 because none would be correctly place.

Find Jerilee's security code from the first 10 randomly generated numbers:

14073

37145

84771

98174

63136

79588

42936

29402

50811

05892

Adapted from Mark Hollis

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Civil Service Candidates - Brain Teaser

There are openings for six civil servant jobs. Thirteen applicants took the civil service exam. Each passes with equally high scores. The administrators decided to give them a second test. This test had only five questions. Each had a Yes/No answer.

Each of the thirteen candidates had a different sequence of answers. The six with the highest scores all had the same number of correct answers. They got the jobs.

Three of the candidates who did not get hired had these sequences of answers:

No, No, Yes, No, No

Yes, No, No, Yes, Yes

Yes, Yes, Yes, No, Yes

What was the correct sequence of answers?

--New Scientist

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Five Cube Calendar - Brain Teaser

There are five cubes whose sides are either numbers or letters. Together they can be used to display any day of the year in this format: 14DEC.

The first two cubes contain the dates. Each face has one digit. One is used for both 6 and 9. Arranging these two cubes will result in any date from 01 to 31. Also, for one of the cubes, the sum of the digits is a perfect square.

The other three cubes have a letter on each face. There are no repeated letters. They can be arranged so that the front faces will display the first three letters of each month. The exception is August which is displayed as VAC. (Many people are on vacation during that month.)

What are on the faces of each cube?

--New Scientist

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How Many Knights - Brain Teaser

In the game of chess, the knight moves two squares in one direction and one in the other direction. It will end up in the diagonally opposite position of a 2 X 3 grid. The squares between the original position and ending position can be occupied.

Find the maximum number of knight pieces that can be positioned on an 8 X 8 square chess board where no knight threatens one of the others, that is, could move into a square occupied by one of the other knights.

Also, in what position is each of the knights?

Thank you, Daryl Cooper

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New Phone Number - Brain Teaser

Mr. Meek loves his new phone number because the last four digits, the extension, have the middle two digits the same, which is just like his name.

Those middle two digits also happen to be the same as the first digit of Mr. Shy's extension.

And the first digit of Mr. Meek's extension is the same as the first digit of Mr. Quite's extension.

If you exchange the first and last digits of Mr. Quite's number, you get Mr. Shy's number.

If you subtract Mr. Quite's number from Mr. Shy's number, you get Mr. Meek's.

What is Meek's new number?

-- New Scientist

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Tricky Triangle - Brain Teaser

The triangle pieces in the drawing below are the same size in both pictures.

Where does the extra space come from?

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Hole in the Rug - Brain Teaser

Your grandmother has a 9' x 12' rug, but due to an unfortunate accident, it has an 8' long hole in the center. Can you make two cuts and piece it together to make a perfect 10' x 10' rug?

Make only two cuts.

HINT: The cuts are not necessarily straight.

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