Next in the Sequence

Here is a series of numbers. What is the next number in the sequence?

1
11
21
1211
111221
312211

13112221

The next number in the series counts the previous numbers. Thus the first number is 1, which is one 1, or 11. To describe 11, you have two 1’s, or 21. Now you have one 2 and one 1, so the next number is 1211. The solution is to continue describing the previous number using only numbers.

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The Old Man’s Book

Milton shuffled slowly along the shelves browsing books. He finally walked up to the counter and handed the girl a book. She looked at the inside cover and told him it would be $3.75. Milton handed her the money and walked away without the book. The girl watched him leave empty-handed but didn’t try to stop him. Why?

Milton was a forgetful and naughty fellow. He was summoning his courage to approach the counter to return his overdue book. The kindly lass at the counter saw the book was 15 days overdue and had accrued the egregious late fee of $3.75 (25 cents a day). Lesson learned, Milton never returned a book late again.

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A Special Something Shared

The numbers 3, 7, 8, 40, 50 and 60 all share something that no other whole number does. What is it?

When spelled out in English they each have exactly five letters.

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Falling Window Cleaner

A window cleaner is cleaning a window on the 25th floor of a skyscraper when he slips and falls. He has no safety equipment and nothing to soften his fall, yet he is not hurt. How can this be?

He was cleaning the inside of the window.

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At Least One is a Boy

A couple has two children. At least one of them is a boy. Assuming the probability of having a boy or girl is 50%, what is the probability that both children are boys?

If you answered 1/2, you’re not without comrades, but the generally accepted answer by statisticians (though not without debate) is 1/3. This is because there are four possible combinations: boy-boy, boy-girl, girl-boy and girl-girl. Since we are told one of the children is a boy (but we don’t know if it’s the first or second child), we can rule out the girl-girl combination, leaving three remaining options. Only one out of 3 is boy-boy, so we get a 1/3 chance.

This is a well-known problem known as the Boy or Girl paradox. The other variation is this brain teaser.

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Ex-Spouse’s Former Daughter-In-Law

What do you call your ex-spouse’s former daughter-in-law’s first husband’s daughter?

You can call them whatever you want, but they have no familial relationship to you.

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Letter Missing From a Series

What letter is missing from this series?
B C D G P T V Z

The letter E. The series contains all of the letters that rhyme with bee (apologies to any English speakers who pronounce Z as zed instead of zee if this confused you).

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The Same Upside Down

A word of five letters,
Upside down is the same,
A shark does this,
But it’s not to blame.

What is the word?

SWIMS.

If you turn the word upside down it’s the same word (the W and M flip to resemble themselves). A shark swims to attack, but it’s not bad. Sharks are just trying to eat. I’d still recommend you swim away if you see one swimming toward you.

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All Words From Nine Letters to One

What 9-letter word can have a letter removed to make a new word and repeat the process until a single letter remains?

startling
starting
staring
string
sting
sing
sin
in
i

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Don’t Get a Goat

On a game show there are three closed doors – one hides a car and the other two conceal a goat. The contestant selects a door, which remains closed, and the host, knowing where the car is hidden, reveals a goat behind one of the remaining two doors. The contestant is then given the option to switch doors or stay with the one they originally selected. What should the contestant do to have the best chance of winning the car?

The contestant should switch doors, which doubles the chance of winning the car. Initially there is a 2/3 chance of picking a goat, but once the other goat is revealed, switching to remaining door gives the contestant a better chance of winning the car. This is known as the Monty Hall Problem and can be very unintuitive.

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