Five Three Two

What is the answer to the last equation?

5 3 2 = 151012
9 2 4 = 183662
8 6 3 = 482466
5 4 5 = 202504
7 2 5 = ?

10000 × (x × y) + 100 × (x × z) + transpose_digits(x × y + y × z)

transpose_digits() just swaps the digits

Posted in Brain Teasers

Always Hungry, Must Be Fed

I am always hungry,
I must always be fed,
The finger I touch,
Will soon turn red

Fire

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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As Long As They’re Dead

This is a place. The first letter is after A and before Z but nowhere in between. You can bring as many people as you want, as long as they’re all dead. Where is it?

The cemetery. The letter C is after A and before Z, and it’s not found in the word “between”. The cemetery won’t take live ones. Fortunately I don’t speak from experience on that.

Posted in Riddles

Painting a Bigger Room

A painter needed 3 days to paint a room. How long would it take him, working at the same rate, to paint a room twice as large (twice the width and twice the height)?

12 days because the walls would be four times as big as the first room.

If the walls are 10 ft x 10 ft, then each wall has 100 square feet. Adding the four walls makes 400 square feet to paint. Doubling the width and height of the walls to 20 ft x 20 ft means each wall is now 400 square feet, for a total of 1600 square feet to paint. 1600 ft is four times 400 square feet, thus if it took him 3 days to paint 400 square feet, it will take 12 days (or four times as much) to paint 1600 square feet.

Posted in Brain Teasers

I Am Here, I Am There

I am here, I am there
I am burned into the mind of none
I walk on fire and live on ice
My words are meaningless for I talk not
I hate everyone yet fear no one
I have lived for centuries
Yet I have never existed
What am I?

Nothingness.

Posted in Riddles

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.

Posted in Brain Teasers

Have No Face

I turn my head and you may go where you want.
I turn it again, you will stay till you rot.
I have no face, but I live or die,
By my crooked teeth.

What am I?

A key

Posted in Riddles

Fly In The Ear

One evening a man is walking home from work and an insect flies into his ear. He tries to pry it out but it doesn’t work. Shaking his head isn’t successful either. Finally he managed to get it out. How did he do it?

As soon as he got home, he shined a flashlight close to his ear and the insect, attracted by the light, flew toward it.

Posted in Brain Teasers

Stink When Alive

I stink when I’m alive, but I smell good when I’m dead. What am I?

A pig. Mmm, ham and bacon…

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