Bank Wait Times

Suppose a small bank has one teller and customer transactions take 10 minutes on average. With 5.8 customers arriving per hour, what is the expected wait time? What would it be if you added a second teller?

With one teller, customers will wait nearly five hours on average. But adding a second teller makes the wait go down to 3 minutes.

Thanks to John D. Cook for this one.

Posted in Brain Teasers

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

Rude Otto

Hannah, Otto, Todd and Eve were walking down the street. Suddenly Otto rudely told Todd he was an outsider and didn’t belong. What made Todd different?

Todd is not a palindrome.

Posted in Brain Teasers

My First Wears My Second

My first wears my second; my third might be
What my first would acquire if he went to the sea.
Put together my one, two, three
And the belle of New York is the girl for me.

Manhattan. A MAN wears a HAT, and a MAN might acquire a TAN if he went to sea.

Posted in Riddles

I’m Yours, But Used More By Others

I belong to you, but am used more by others.

What am I?

Your name. It could also be your phone number.

Posted in Riddles

What Can Be Swallowed

What can be swallowed, But can also swallow you?

Pride.

Posted in Riddles

I Stand Like A Sentry

I stand like a sentry
And am barred by the gentry,
The first month and its god oft slip
Between my hard, dun colored lip.

What am I?

Sentries are posted at borders, gates, or doors.
The gentry (in this case to referring to the general populace) bar their doors at night.
The first month is January, named after the Roman god Janus, the double-faced God of doorways, passages and thresholds.
You pass through the doorway (hence the slip), and dun is a brown color, referencing the color of wood, which most doors are made of. Though it’s not commonly referred to, the “lip of the door” is the part of the door that fits into the doorframe on the handle/knob side, particularly if the door is lipped or ridged in order to fit the door frame better.

Thanks to Helena for creating this and sending it in.

Posted in Riddles
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Short Black Dress

In the day I stand tall in a white petticoat. By evening I’m in my short black dress. What am I?

The wick of a candle.

Posted in Riddles

Not Seen Nor Felt

It cannot be seen, cannot be felt,
Cannot be heard, cannot be smelt.
It lies behind stars and under hills,
And empty holes it fills.
It comes first and follows after,
Ends life, kills laughter.

The darkness.

Posted in Riddles

You’ll Have At Night

You’ll have this six-letter word at night and if you remove the first letter it denotes the top, such as on a train. What is the word?

Supper (upper).

Posted in Riddles