Three Items for $100

Bill buys three items at the store for exactly $100. The second item costs half as much as the first item, and the third item is half as much as the second.

How much did each one cost?

First: $57.14
Second: $28.57
Third: $14.29

Posted in Brain Teasers

What is the First Number of the Sequence?

If a number in a numeric sequence is 17 and the second number is 3, what is the first number?

I hesitated to add this because it’s poorly worded, ambiguous and the answer could be almost anything. I prefer teasers with a single answer, but there you go.

If you came up with a different answer and can explain how you did it, don’t think you’re wrong. It’s probably just as valid. Feel free to share yours in the comments.

My answer for the first number is 2.

Here’s how I got it.

The generic rule for a number in the sequence is: 2^(n – 1) + 1, where n is the position in the sequence.

Note: The teaser doesn’t specify the position of 17. In this case, it’s fifth.

Position 1: (so n = 1) is 2^(1 – 1) + 1 = 2

Position 2: 2^(2 – 1) + 1 = 3

Position 3: 2^(3 – 1) + 1 = 5

Position 4: 2^(4 – 1) + 1 = 9

Position 5: 2^(5 – 1) + 1 = 17

For the curious, the next 5 numbers of the sequence would be:

Position 6: 2^(6 – 1) + 1 = 33

Position 7: 2^(7 – 1) + 1 = 65

Position 8: 2^(8 – 1) + 1 = 129

Position 9: 2^(9 – 1) + 1 = 257

Position 10: 2^(10 – 1) + 1 = 513

Posted in Brain Teasers

What Do You Serve?

What do you serve that a polite recipient would immediately send back?

A ball, when you’re playing tennis, volleyball, table tennis, etc.

Posted in Riddles

Before Mount Everest

Before Mt. Everest was discovered, what was the tallest mountain in the world?

Still Mount Everest. Just because it wasn’t discovered didn’t make it any smaller.

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Jim and Wanda’s Apples

Jim and Wanda both have some apples. If Jim gives Wanda an apple, they will both have the same number of apples. However, if Wanda gives Jim an apple, Jim will have twice as many as Wanda. How many apples do Jim and Wanda each have?

Jim has 7 apples and Wanda has 5 apples.

Posted in Brain Teasers

Asks But Never Answers

What asks but never answers?

An owl.

Posted in Riddles
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Thin, Bold, Sick And Cold

One thin, one bold,
One sick, one cold.
The earth we span,
To prey upon man.

Who are we?

The Four Horsemen of the Apocalypse.

Posted in Riddles

What is the Chance That You’ll Be Correct?

If you choose an answer to this question at random, what is the chance that you will be correct?

a) 25%
b) 50%
c) 60%
d) 25%

This is becomes a self-referential paradox. Both A and D would be correct if there were four unique answers, but since A and D are the same answer, the chance that you would choose a correct answer is 50%, which makes B correct. But if there’s only one correct answer, the odds of choosing the correct one at random goes back to 25%. And around and round you go.

There’s a lot of discussion at Richard Wiseman’s blog and more at Lifehacker, where I first saw this.

Posted in Brain Teasers

The Long River

How many times does the letter S appear in the name of the longest river in the world?

Zero. The Nile is the longest river in the world. Some claim the Amazon as the longest, but that too has no “S”es (that looks weird but I don’t know how else to write the plural of “s”). The Mississippi is the 4th largest river in the world according to a href=”https://en.wikipedia.org/wiki/List_of_rivers_by_length”>Wikipedia.

Posted in Riddles

In A Dark Room with a Rope and a Pencil

Imagine you are in a dark room with a locked door. All you have with you is a rope and a pencil. You can hear the rain outside, but there
are no windows. How do you get out?

Stop imagining.

Posted in Riddles
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