Two Fuses

You have a lighter and two fuses that take exactly one hour to burn, but they don’t burn at a steady rate. For example, one fuse could take 59 minutes to burn the first inch and then burn the rest of the fuse in the last minute.

How would you use these two fuses to measure 45 minutes?

Light the first fuse on both ends and the second fuse at only one end. When the first fuse burns out you know 30 minutes have passed. Light the other end of the second fuse and when it burns out, 45 minutes have passed.

Posted in Brain Teasers

False Positive HIV Test

Imagine an HIV test that is 95% accurate (false positive rate of 5%) and around 2% of the tested population is infected with HIV. What is the probability that you actually have HIV when your test comes back positive?

29%

To read more about this, see the False Positive Paradox page on Wikipedia.

Posted in Brain Teasers

Soldiers Line Up Spaced With Pride

Soldiers line up, spaced with pride,
Two long rows lined side by side,
One sole unit can decide,
If the rows will unite or divide.

What am I?

A zipper.

Posted in Riddles
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Dark Halloween Night

On a dark, stormy Halloween night, four kids named Luke, John, Sarah and Bob walk into a haunted house during a blackout. Only one can escape. They take a staircase to the second floor, a trapdoor on the left, then go up the ladder to the right, followed by a 28-foot slide to the basement through the mouth of a Giant Panda. In one corner of the murky cellar is a chainsaw, a dagger, a rope with a noose and an electric chair. Written on the wall in blood are the words, “Only one will survive – choose your death!” Bob takes the rope, Sarah picks up the dagger, John chooses the chainsaw and Luke uses the chair.

Who survives?

Luke, because there’s no power (it’s during a blackout).

Posted in Brain Teasers

Word Jumble

Frederick takes half of CONNIE, part of NESTA, part of NELLIE and part of AUNTIE to create something new. What does he call his new creation?

Constantine

Posted in Brain Teasers

A Big Pizza Pie

To get the most pizza, should you order two 12″ pizzas or one 18″ pie?

One 18″, with ~255 sumptuous square inches. Two 12″ pizzas would only give you ~226 square inches.

Note: The area of a circle is = πr2.

Posted in Brain Teasers

Laughter Between Breakfast And Tea

People speak through me, yet I do not make a sound.
People can sell me, yet I have many clones.
I can bring you laughter between breakfast and tea,
Yet I can also break your heart easily.
I cover the earth like trees of old,
Whose leaves can blind and yet enfold.

A book. Authors can speak to you through a book, yet the book makes no sound. Books are sold and have many duplicate copies. A book can bring the reader to tears and laughter, they span the globe and the leaves of a book (a single sheet in a book is called a leaf) can get you wrapped up in the story that you’re unaware of what’s going on around you.

Posted in Riddles

Find The Hidden Cities

Wallace died a wealthy, if somewhat odd, man without any living relatives. He left his money in four different cities for the first four people who could find it. The only clue he left was this poem:

Do not go solo,
Pairs up with a friend,
Though I hasten to add,
I’ll avenge my end.

What are the four cities?

Anagrams of four cities can be found in the poem.

Oslo (solo)
Paris (pairs)
Athens (hasten)
Geneva (avenge)

Posted in Brain Teasers

Short Black Dress

In the day I stand tall in a white petticoat. By evening I’m in my short black dress. What am I?

The wick of a candle.

Posted in Riddles

Split Itself

What can split itself
before splitting something else?

Lightning. It looks like it’s splitting apart in the sky, and trees are split in half when struck by lightning.

By Sef Daystrom

Posted in Riddles