Rebellious Randall

You’re waiting to board your flight at the airport with 99 other passengers, each with an assigned seat. All but one of the passengers will gladly sit in their designated seat. The only exception is Randall, a scoundrel who refuses to follow the rules. When he boards, he will choose a random, unoccupied seat.

If a rule-following passenger finds someone in their spot, they will choose another one at a random from the remaining unoccupied seats.

What is the probability that the last person to board the plane will sit in their proper seat?

The randomness stops as soon as someone else sits in Randall’s assigned seat. The chances of this happening range from 1 out of 99 to 1 out of 1 (when only one seat remains).

Thus, the probability of the last person sitting in their own seat can be calculated as 1/99 plus the sum of 2 to 98 of the formula 1 / n × (n + 1), which works out to 0.5, or 50%.

So there’s a 50% chance the last passenger will sit in their own seat thanks to Randall for screwing up order and procedure when boarding an aircraft.

Posted in Brain Teasers

Counting Your Presents

According the song “The Twelve Days of Christmas”, how many total gifts were received?

364. Here’s the explanation.

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Add More But Weigh Less

The 17 items in your shopping cart weigh 8 pounds. But when your daughter puts in a ball, poster board and yo-yo the shopping cart weighs less. How is that possible?

Your daughter had to get out of the cart to fit the remaining items.

Posted in Brain Teasers

Asleep, Parts, Ideals Trianagrams

Rearrange the letters of the first word to form a new one, then rearrange the letters of the new word to form a third.

ASLEEP _ _ _ _ _ _ _ _ _ _ _ _
PARTS _ _ _ _ _ _ _ _ _ _
IDEALS _ _ _ _ _ _ _ _ _ _ _ _

1. ASLEEP, PLEASE, ELAPSE
2. PARTS, TRAPS, STRAP (TARPS or SPRAT also work)
3. IDEALS, SAILED, LADIES

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Ancient Arabic

I’m Arabic, but if you speak English, you probably use me every day.

What am I?

The Arabic numerals, 1, 2, 3, etc.

Posted in Riddles
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New Door

Rearrange the letters in the words “new door” to make one word.

“new door” can be rearranged into “one word”

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Seemingly Simple Math

What is the answer to this math problem:

8 ÷ 2 (2 + 2)

16 or 1, depending.

According to PEMDAS, parentheses come first: 8 ÷ 2 (4)

Then, even though multiplication is first in PEMDAS, you go left to right: 4 (4) = 16

If you got 1, you’re in good company. That’s what I got at first too but most calculators I’ve tried get 16.

I found this at Popular Mechanics and the debate continues online.

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Kevlar, Fire Escapes and Wipers, Oh My!

What do computer compilers, kevlar, fire escapes and windshield wipers all have in common?

They were all invented by women.

A variation of this brain teaser includes laser printers (they were invented by Gary Starkweather) and bulletproof vests (invented by Casimir Zeglen using silk, though modern vests use Kevlar, so it’s halfway right).

Posted in Brain Teasers

Swallowed the Dead

I’ve swallowed the dead,
Of a torn land’s end.
And I hold the remains,
Of an unknown friend

A mansion once stood,
Where I now lay,
We honor all those
Who gave us today.

What am I?

Arlington National Cemetery, the burial place of soldiers from the United States Civil War. It also houses the tomb of unknown soldiers. General Robert E. Lee’s mansion once stood on the land that is now occupied by the cemetery. And on Memorial Day in the US, we honor all those who died while serving their country’s armed forces.

Posted in Riddles
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Hilda’s Age

When Randolph asked Hilda how old she was, Hilda replied that in two years she would be twice as old as she was five years ago. How old is Hilda?

Aside from the potential response that it’s rude to ask the age of a lady, the answer can be worked out mathematically.

x + 2 = 2(x – 5)
x + 2 = 2x – 10
x + 12 = 2x
12 = x
In two years she’ll be 14, which is twice her age 5 years ago (7).

Posted in Brain Teasers