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

Four Times Every Week

What happens four times in every week, twice in every month and once in a year?

The letter ‘e’. There are four ‘e’s in ‘every week’, two ‘e’s in ‘every month’ and one ‘e’ in ‘year’.

Posted in Riddles

Garlic or Spice

Before any changes I’m a garlic or spice. My first is altered and I’m a hand-warming device. My second is changed and I’m trees in full bloom. The next letter change makes a deathly old tomb. Change the fourth to make a fruit of the vine. Change the last for a chart plotted with lines. What was I? What did I become? What did I turn out to be?

clove
glove
grove
grave
grape
graph

Posted in Riddles

The Long River

How many times does the letter S appear in the name of the longest river in the world?

Zero. The Nile is the longest river in the world. Some claim the Amazon as the longest, but that too has no “S”es (that looks weird but I don’t know how else to write the plural of “s”). The Mississippi is the 4th largest river in the world according to a href=”https://en.wikipedia.org/wiki/List_of_rivers_by_length”>Wikipedia.

Posted in Riddles

The Bookworm

A bookworm eats from the first page of an encyclopedia to the last page in a straight line. The encyclopedia consists of ten 1000-page volumes and is sitting on a bookshelf in the usual order. Not counting covers, title pages, etc., how many pages does the bookworm eat through?

        __                             __
      B|  |                           |  |F
      A|1 |...........................|10|R
      C|  |                           |  |O
      K|  |                           |  |N
       |__|                           |__|T
      -------------------------------------

On a book shelf the first page of the first volume is on the “inside”, so the bookworm eats only through the cover of the first volume, then 8 times 1000 pages of Volumes 2 – 9, then through the cover to the 1st page of Vol 10 for a total of 8,000 pages.

Note: The question asks how many pages, not how many sheets of paper.

Posted in Brain Teasers

I’ll Always Smile Back

If you drop me I’m sure to crack but give me a smile and I’ll always smile back

A mirror.

Posted in Riddles

I A N Rebus

What does the following rebus represent?

I           A
      N
R           B

Scatterbrain.

Posted in Riddles
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Twenty One Points Divide And Dance

Twenty one points divide and dance,
Twirling and leaping about,
Ladies, Romans and knights of France,
Craving a victor’s rout,
Wrought of wood, ivory or bone,
An exciting yet vicious pursuit,
Ancient, forbidden and crooked,
All in search of the loot.

A die. The standard die has 21 pips (or points), divided up on the six sides of the die which dance around when rolled. Ladies, knights and Romans all played dice as a pastime (though not together). Dice can be made of wood, ivory and bone, among other materials. Dice have been used in Asia since before recorded history and many governments tried unsuccessfully to outlaw the game. Professional gamblers were common and often used loaded dice. Desperate German chaps even bet their own liberty on a single roll of the dice.

Posted in Riddles

What Holds Two People Together?

What holds two people together but touches only one?

A wedding ring.

Posted in Riddles

What Has Roots Nobody Sees?

What has roots that nobody sees,
Is taller than trees,
Up, up it goes,
Yet it never grows?

A mountain (from Tolkien)

Posted in Riddles