Puzzle

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Trefoil puzzle #175: Tennis balls

Seven tennis balls are identical in every way, except that one of them weighs slightly less than the other six. Using a balancing scale, what is the smallest number of weighings that are required to identify the lighter ball?

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Trefoil puzzle #174: Riddle your mind

  1. A square house has 4 walls. All of the walls are facing south, and a bear is circling the house. What colour is the bear?
  2. What starts with “e”, ends with “e” and contains one letter?
  3. Once you have it, you want to share it. Once you share it, you don’t have it. What is it?

Once you’ve solved the riddles, send us your answers on Facebook – we look forward to hearing from you!

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Trefoil puzzle #172: Frequent numbers

What digit is the most frequent between the numbers 1 and 1,000 (inclusive)? To solve this riddle you don’t want to manually do all of the maths but rather try to figure out a pattern.

Once you’ve solved the puzzle, send us your answer on Facebook – we look forward to hearing from you!

 

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Trefoil Puzzle #171: A plane crash

A flight from Tokyo to London, carrying 120 Japanese tourists, crashes on the Lithuanian / Latvian boarder. Where should the authorities bury the survivors?

Once you’ve solved the puzzle, send us your answer on Facebook – we look forward to hearing from you!

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Trefoil puzzle #169: A frog and a well

Freddie is a very clumsy frog.
Freddie falls to the bottom of a well which is 30m deep.
Every day, Freddie works really hard to climb up the well and climbs 3m.
Every night, Freddie slips down 1m.
How many days would it take Freddie to escape from the well?

Once you’ve solved the puzzle, send us your answer on Facebook – we look forward to hearing from you!

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TREFOIL PUZZLE #168: Ants and a triangle

Three ants are sitting at the three vertices of an equilateral triangle. Each ant randomly picks a direction and starts to move along the edge of the triangle. Assuming that all the ants move at the same speed, what is the probability that none of the ants collide?

Once you’ve solved the puzzle, send us your answer on Facebook – we look forward to hearing from you!

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TREFOIL PUZZLE #167: The Oscars puzzle

The film “The Shape of Water” was nominated in 13 categories this year and won four Oscars.

Assuming that each award category has a total of five contestants, and assuming that each contestant is equally likely to win, what is the probability that “The Shape of Water” wins four or more Oscars?

Once you’ve solved the puzzle, send us your answer on Facebook – we look forward to hearing from you!

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Trefoil Puzzle #166: Airplane seats

People are waiting in line to board a 100-seat airplane. Steve is the first person in the line. He gets on the plane but suddenly can’t remember what his seat number is, so he picks a seat at random. After that, each person who gets on the plane sits in their assigned seat if it’s available, otherwise they will choose an open seat at random to sit in.

The flight is full and you are last in line. What is the probability that you get to sit in your assigned seat?

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