Rotating Coins Around Coins

You have two coins of equal size on a table, situated end to end vertically. If you roll the top coin around the bottom coin until it returns to its original position, how many times will it have rotated?

Twice. See this video for more details.

Posted in Brain Teasers

Wily Winifred and the Case of the Odd Numbers

Mrs. Shine was having a rough day and wanted a break. So she asked her class to calculate the sum of the first 50 odd numbers. In a few moments, Winifred was at her desk with the correct answer of 2,500. Stunned, Mrs. Shine figured she must have gotten lucky, and sent precocious Winifred back to her seat with the task of finding the sum of the first 75 odd numbers. Again, Winifred returned in seconds with the correct answer (5,625).

How did Winifred find the answer so quickly?

Winifred, being the precocious child she is, realized there was a pattern when computing smaller sums of odd numbers.

First 3: 1 + 3 + 5 = 9
First 4: 1 + 3 + 5 + 7 = 16
First 5: 1 + 3 + 5 + 7 + 9 = 25

Do you see the pattern like our dear friend Winnie?

For the first n odd numbers, the sum is equal to n2. Thus the first 50 is 502, or 2,500, and the first 75 is 752, or 5,625.

Posted in Brain Teasers

The More There Is The Less You See

The more there is the less you see. What is it?

Darkness

Darkness.  There more darkness there is, the less you can see.

Posted in Riddles
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Loud Noise When Changing Its Jacket

What makes a loud noise when changing its jacket, becomes larger but weighs less?

Popcorn.

Posted in Riddles

An Elevator Accident

I’m in an elevator with two other people. When it reaches the first floor, one person gets out and six get in. When it reaches the second floor, three people get out and twelve get in. At the third floor, five leave and nine enter. It rises to the fourth floor, one person gets on and the doors close. Suddenly, the elevator cable snaps and the car smashes to the ground. No one survives the fall, yet I’m alive and know exactly how many people go on and off the elevator at every floor. How is this possible?

I got off at the first floor. I’m a security guard and knew how many people got on and off the elevator by watching the surveillance footage.

Posted in Brain Teasers

Which Is The Odd Word Out?

Which of the following words is the odd one out?

Chocolate
Biscuit
Lemonade
Jelly
Cake

Lemonade. It’s the only drink in the list.

Posted in Brain Teasers

Two Three Ten Sequence

If:
2 3 = 10
7 2 = 63
6 5 = 66
8 4 = 96
9 7 = __

What is the missing number?

f(n, m) = (n + m) × n

e.g. f(2, 3) = (2 + 3) × 2 = 10

Hence, f(9, 7) = (9 + 7) × 9 = 144

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I Am Two-faced, But Bear One Head

I am two-faced, but bear one head.
Men spill their blood for me.
I have no legs but travel widely.
I make kings immortal.
I am potent when shared,
Yet lust for my power keeps me locked away.

What am I?

Money (coins specifically). Coins have two faces, heads and tails. People fight for money, and money travels far and wide. Kings live on when they’re depticted on a coin. Sharing money with others is a meaningful experience yet many people keep their money locked up.

Posted in Riddles

Oct 31 = Dec 25

How can Oct 31 and Dec 25 be the same?

Because Oct 31 represents the octal (base 8) number 31, which, when converted to decimal, is 25. Dec 25 is short for Decimal 25, thus the two are equal.

Posted in Brain Teasers

At The Sound Of Me, Men May Dream

At the sound of me, men may dream
Or stamp their feet
At the sound of me, women may laugh
Or sometimes weep

Music.

Posted in Riddles